Axis ship-watching activities in the Gibraltar area implemented into the game

[InfArmMot]

Recently I read a few chapters in a book about the German planning to defeat the Gibraltar position. It was pretty detailed. For instance it explained how Franco constantly demanded a high price of corn, in exchange for allowing the Germans to march through Spain. Without his permission they could not attack and Neutralize Gibraltar.

The book also told the story of how the Abwehr had spies positioned on a hotel, on the African side, just across the cliff. How the spies observed every surface vessel passing through the strait and even how the British fortified the cliff. They also observed the incoming and outgoing air crafts. At least during daytime, where the airstrip could be easily seen from across the strait.

From 1939 until January 1944, the intelligence services of Germany and Italy, with the assistance of the Spanish government, maintained a network of stations in the vicinity of the Strait of Gibraltar. The stations tracked the movements of Allied warships and merchant vessels and became a valuable source of intelligence to the Axis, for attacks on Allied convoys. The British Government considered attacking the stations on two occasions during 1942 but decided instead to use diplomatic pressure to have them closed. The stations are believed to have ceased operations in January 1944.

Axis ship-watching activities in the Gibraltar area - Wikipedia

en.wikipedia.org

Suggestion
Shouldn't we incorporate this spy activity into the game. And this goes for if not all, then most straits. Regardless of nation.

 

[ConjurerDragon]

The article on WIKI you linked mentioned how the agents activity was ineffective the first year, better established with infrared detection stations and working 1941-1943 and stopped by Franco for the last two years of the war (1944-1945).

So it is not something you could do for "any strait" as simply sending some agents with a spyglass somewhere would be simple but ineffective, e.g. due to fog, rain, night, distance.

And being able to install real observation stations with technical equipment would require the knowledge and permission of the owning state.

So Franco Spain would allow it - as long as Germany appears to be winning and Spain is going for a "friendly neutrality" towards the Axis.

As a reason not to include it: It is unreliable. England did have a number of coastal observers in their own country and still did not manage to prevent the Channel Dash.

 

[InfArmMot]

Perhaps it could be an option, to invest in a spy operation at certain straits, where a neutral country is located?Besides of Gibraltar, it could be the Danish/Swedish strait, the Strait of Malaccae, the Bospurus strait and so on.

There are plenty of straits on the map, however, it is true that some of them, like Gibraltar, perhaps are too wide (7 kilometers from each side) - but then again, some are narrow enough. Maybe the strait of Gibraltar could be used as a template for how difficult it is to observe a ship passing through. As you mention, rain, fog and darkness can certainly play a role, reducing a ships vissibility.

What would be the maximum distance, that we could agree on, for observing a ship in clear weather? 2, 4, 7 kilometers, or more?

Example on how an event could be made, involving two events

First event:
INVEST IN SHIP WATCHING ACTIVITIES: 200 money
25% chance of spotting convoys
35% chance of spotting navies with 10+ ships

Second event:
INVEST IN SHIP WATCHING ACTIVITIES with Infrared equipment: 450 money
45% chance of spotting convoys
55% chance of spotting navies with 10+ ships

And of course you could also invest in anti spy operations in a certain province adjacent to a strait.


Another wikie link, this one is a list of straits on the world map:

List of straits - Wikipedia

en.wikipedia.org

A

• Agate Pass – between Port Madison and mainland Kitsap County in Puget Sound
• Agattu Strait – between Attu Island and Agattu Island in the Alaskan Aleutians
• Akashi Strait – between the Japanese islands of Honshu and Awaji
• Alas Strait – between Lombok and Sumbawa in Indonesia
• Alor Strait – Lesser Sunda Islands in Indonesia
• Amchitka Pass – between the Rat Islands group to the west and the Delarof Islands to the east within the Alaskan Aleutians
• Anegada Passage – between the Virgin Islands and Anguilla
• Anguilla Channel – between Anguilla and Saint Martin
• Arthur Kill – between Staten Island and New Jersey
• Augusta's Strait – a.k.a. Dampier Strait (Indonesia), between the Raja Ampat islands of Waigeo and Batanta, within the Indonesian province of West Papua

B

• Bab-el-Mandeb – connects the Red Sea to the Gulf of Aden / Arabian Sea
• Bab Iskender – between Yemen on the Arabian Peninsula and Djibouti in Africa
• Balabac Strait – between Palawan, Philippines and Borneo
• Bali Strait – between the Indonesian islands of Java and Bali
• Strait of Baltiysk – between Vistula Bay and Gdańsk Bay
• Bangka Strait – between Sumatra and Bangka Island (also: Banca, Banka)
• Banks Strait – between Cape Barren Island/Clarke Island and Tasmania
• Bashi Channel – between Mavudis (also called Y'Ami Island), Philippines and Orchid Island, Taiwan
• Basilan Strait - between Mindanao, Philippines and Basilan, Philippines.
• Bass Strait – between mainland Australia and Tasmania
• Beagle Channel – Tierra del Fuego
• Strait of Belle Isle – between Newfoundland and mainland Canada
• Bering Strait – between Asia and North America
• Bohai Strait – between Bohai Sea and Yellow Sea
• Bohol Strait – a.k.a. Cebu Strait
• Strait of Bonifacio – between Corsica and Sardinia
• Bosporus – between Europe and Asia
• Bougainville Strait (Indonesia) – between Waigeo and the Kawe Islands[1]
• Bougainville Strait (Solomon Islands) – between Bougainville Island and Choiseul Island
• Boundary Pass – between British Columbia and Washington state
• Bransfield Strait – between South Shetland Islands and Antarctic Peninsula
• Bungo Channel – between Kyūshū and Shikoku in Japan

C

• Cabot Strait – between Newfoundland and Cape Breton Island
• Caicos Passage – between Turks and Caicos Islands and the Bahamas
• Strait of Canso – between Cape Breton Island and mainland Nova Scotia
• Carquinez Strait – connects San Pablo Bay and Suisun Bay, California
• Cebu Strait (a.k.a. Bohol Strait) – between Bohol and Cebu in the Philippines
• Chatham Strait – between Chichagof Island and Admiralty Island, Alaska
• Chios Strait – between Turkey and the Greek island Chios
• Clarence Strait – between Prince of Wales Island and mainland Alaska
• Coco Channel – between the Burmese Coco Islands and the Indian North Andaman Island
• Colvos Passage – Puget Sound
• Cook Strait – between the North Island and South Island of New Zealand
• Straits of Corfu – between the Greek island Corfu and mainland Greece/Albania
• Cozumel Channel – between Cozumel Island and the Yucatán Peninsula, Mexico

D

• Dalcahue Channel – between Quinchao Island and Chiloé Island
• Dalco Passage – Puget Sound
• Dampier Strait (Indonesia) – between Bird's Head Peninsula and Raja Ampat Islands
• Dampier Strait (Papua New Guinea) – between New Britain and Umboi Island
• Danish straits – collectively refers to the Danish straits Oresund, Fehmarn Belt, Little Belt and Great Belt between Scandinavia and Jutland
• Dardanelles – between Europe and Asia
• Davis Strait – between Baffin Island and Greenland
• Deception Pass – Puget Sound
• Denmark Strait – between Greenland and Iceland
• La Désirade Passage – Guadeloupe
• Detroit River – between Lake St. Clair and Lake Erie / and the province of Ontario, Canada, and the state of Michigan, USA (The word "détroit" is French for "strait")
• Dixon Entrance – between Alaska and British Columbia
• Dolphin and Union Strait – between Northwest Territories and Victoria Island
• Dominica Passage – between Dominica and Guadeloupe
• Strait of Dover – the narrowest part of the English Channel between Great Britain and France
• Dragon's Mouths (Bocas del Dragón) – between Trinidad and Venezuela
• Drake Passage – between South America and Antarctica

E

• East River – between Manhattan, the Bronx and Long Island
• Eastern Channel – between Korean Peninsula and the Iki Island
• English Channel – between Great Britain and France
• Euripus Strait – between the Island of Euboea and the Greek mainland on the Aegean

F

• Falkland Sound – between West Falkland and East Falkland
• Fehmarn Belt – between the German island Fehmarn and the Danish island Lolland
• Fehmarn Sound – between German island Fehmarn and the German mainland
• Straits of Florida – between Florida and Cuba
• Formosa Strait – between Taiwan and the Chinese mainland
• Foveaux Strait – between the South Island and Stewart Island of New Zealand
• Fury and Hecla Strait – between Baffin Island and Melville Peninsula

G

• Galowa Strait – a.k.a. Sele Strait
• Strait of Georgia – between Vancouver Island and mainland British Columbia, Canada
• Strait of Gibraltar – between Europe and Africa
• Golden Gate Strait – between Marin County, California and San Francisco – entrance to San Francisco Bay
• Great Belt – between the islands of Zealand and Funen in Denmark
• Guadeloupe Passage – north of Guadeloupe, West Indies
• Gulf of Corryvreckan - between the Scottish islands of Jura and Scarba
• Gulf of Mannar – between India and Sri Lanka
• Gulf Trough (a.k.a. Suwannee Strait) – (prehistoric)

H

• Hall Basin – between Ellesmere Island and Greenland
• Harlem River – between Manhattan and The Bronx
• Haro Straits – series of straits between British Columbia and Washington state
• Hecate Strait – between Haida Gwaii and British Columbia
• Honguedo Strait – between Anticosti Island and Gaspé Peninsula in Quebec
• Strait of Hormuz – between Oman and Iran
• Hōyo Strait – between Kyūshū and Shikoku in Japan
• Hudson Strait – between Baffin Island and Quebec

I

• Irbe Strait – between Latvia and the island of Saaremaa in Estonia

J

• Jamaica Channel – between Jamaica and Hispaniola in the Caribbean
• Jildo Strait – somewhere around Waigeo[2] (same as Jailolo Strait?[3])
• Johor Strait or Strait of Johor – between Singapore and the state of Johor of Malaysia
• Strait of Juan de Fuca – between Vancouver Island, Canada and Olympic Peninsula, United States

K

• Kalmar Strait – between Öland and Småland
• Kane Basin – between Ellesmere Island and Greenland
• Kanmon Strait – between Honshū and Kyūshū
• Kara Strait – between Novaya Zemlya and Vaygach Island in Russia
• Karimata Strait – between Sumatra and Borneo
• Kattegat – between Danish Jutland and Swedish Halland and neighboring provinces.
• Kerch Strait – between Crimea and Russia
• Kill Van Kull – between Staten Island and Bayonne, New Jersey
• Kitan Strait – between Awaji Island and the island Honshū in Japan
• Korea Strait – between Korea and Japan
• Gulf of Kuşadası – between Turkey and the Greek island Samos
• Kvarken – between Sweden and Finland
• Kwangtung Strait

L

• Langeland's Belt – between Danish islands of Langeland and Lolland
• Little Belt – between the island Funen and mainland Denmark
• Lombok Strait – between Bali and Lombok in Indonesia
• Luzon Strait – between Taiwan and Luzon, Philippines

M

• Straits of Mackinac – between Lake Michigan and Lake Huron / and between Michigan's Upper and Lower Peninsulas
• Main Channel – between Lake Huron and Georgian Bay / and between Ontario's Manitoulin Island and the Bruce Peninsula
• Strait of Magellan – between South America and Tierra del Fuego
• Makassar Strait – between Borneo and Sulawesi
• Malacca Strait or Strait of Malacca – between Peninsular Malaysia and Sumatra
• Maliku Kandu – Maldives
• Malta Channel – between Malta and Sicily
• Mare Island Strait – between Mare Island and mainland Solano County in California
• Marie-Galante Passage – Guadeloupe
• Martinique Channel – between Saint Vincent and the Grenadines and Grenada
• Martinique Passage – between Dominica and Martinique
• McClure Strait – Melville Island and Banks Island
• Menai Strait – between Anglesey and mainland Wales
• Strait of Messina – between Sicily and mainland Italy
• The Minch – between Outer Hebrides and mainland Scotland
• Mindoro Strait – between Mindoro and Palawan in the Philippines
• Mona Passage – between Hispaniola and Puerto Rico
• Myeongnyang Strait – between Jindo Island and mainland South Korea
• Mytilini Strait – between Turkey and the Greek island Lesbos

N

• Nares Strait – between Ellesmere Island and Northern Greenland and connects Baffin Bay with Lincoln Sea / the Arctic Sea
• The Narrows – between Staten Island and Brooklyn in New York City
• Naruto Strait – between Awaji Island and the island Shikoku in Japan
• Nemuro Strait – between Kunashir Island and the Shiretoko Peninsula in Hokkaidō, Japan
• Niagara River – between Lake Erie and Lake Ontario / and the province of Ontario, Canada, and the state of New York, USA
• Nicholas Channel – between Cuba and the Bahamas
• North Channel – between Northern Ireland and Scotland
• Northumberland Strait – between Prince Edward Island and New Brunswick/Nova Scotia

O

• Old Bahama Channel – between Cuba and the Bahamas
• Ombai Strait – Alor Archipelago, Indonesia
• Øresund – between Danish Zealand and Swedish Scania
• Strait of Otranto – between Italy and Albania

P

• Palk Strait – between India and Sri Lanka
• Panama – between North America and South America (Panama Canal)
• Pearse Canal – between Alaska and islands of British Columbia
• Pentland Firth – between the Orkney archipelago and the mainland of Scotland
• La Pérouse Strait (also Soya Strait) – between Sakhalin and Japan
• Pertuis d'Antioche – on the Atlantic coast of Western France
• Pickering Passage – Puget Sound
• Pitt Strait (Indonesia) (a.k.a. Sagewin Strait) – between Salawati and Batanta in Indonesia
• Pitt Strait (New Zealand) – between Chatham Island and Pitt Island in the Chatham Islands
• Port Washington Narrows – Puget Sound
• Porte des Morts – between Green Bay and Lake Michigan
• Prince of Wales Strait – between Banks Island and Victoria Island in Canada

Q

• Qiongzhou Strait – Hainan and Guangdong

R

• Revenges Strait – a.k.a. Sele Strait
• Rich Passage – Puget Sound
• Robeson Channel – between Ellesmere Island and Greenland

S

• Sagewin Strait – a.k.a. Pitt Strait (Indonesia)
• Saint-Barthélemy Channel – between Saint Barthélemy and Saint Martin
• St. Clair River – between Lake Huron and Lake St. Clair / and the province of Ontario, Canada, and the state of Michigan, USA
• St George's Channel – between Ireland and Wales
• St George's Channel – between New Britain and New Ireland in the Bismarck Archipelago
• Saint Lucia Channel – between Martinique and Saint Lucia
• St. Marys River – between Lake Superior and Lake Huron / and the province of Ontario, Canada, and the state of Michigan, USA
• Saint Vincent Passage – between Saint Vincent and Saint Lucia
• Les Saintes Passage – Guadeloupe
• Sakonnet River – between Aquidneck Island and Tiverton and Little Compton, Rhode Island.
• San Bernardino Strait – between Luzon and Samar in the Philippines
• San Juanico Strait – between Samar and Leyte islands in the Philippines
• Scapa Flow – between several of the Orkney islands
• Sele Strait (a.k.a. Galowa Strait, Revenges Strait) – between Salawati and New Guinea
• Serpent's Mouth (Boca del Serpiente) – between Trinidad and Venezuela
• Shelikof Strait – between mainland Alaska and Kodiak Island
• Sibutu Passage – between Borneo and the Sulu Archipelago
• Strait of Sicily – between Sicily and Africa
• Singapore Strait – between Singapore and Indonesia (Sumatra)
• Skagerrak – separating Denmark from Norway and Sweden
• Smith Sound – between Ellesmere Island and Greenland
• The Solent – between the Isle of Wight and southern Great Britain
• The Sound or Øresund – between Denmark and Sweden
• South Kvarken – between the Finnish Åland Islands and Sweden
• Soya Strait or La Pérouse Strait – dividing Sakhalin (Karafuto) from Hokkaidō
• Sumba Strait – between Flores and Sumba, Indonesia
• Sunda Strait – between Sumatra and Java
• Surigao Strait – between Leyte and Mindanao islands in the Philippines
• Suwannee Strait (prehistoric) – a.k.a. Gulf Trough
• Svinesund – between Norway and Sweden
• The Swale – between the Isle of Sheppey and southern Great Britain

T

• Tablas Strait – between Mindoro and Panay islands in the Philippines
• Tacoma Narrows – Puget Sound
• Taiwan Strait – between Taiwan and Mainland China
• Tanon Strait – between Negros and Cebu islands in the Philippines
• Strait of Tartary (also Mamiya Strait and Strait of Nevelskoi) – Sakhalin
• Strait of Tebrau – between Peninsular Malaysia and Singapore
• Strait of Tiran – between the Sinai peninsula and Saudi Arabia
• Tolo Channel – narrow opening to the Tolo Harbour in Hong Kong
• Tongass Passage – between Alaska and British Columbia
• Torres Strait – between New Guinea and Australia
• Tsugaru Strait – between Hokkaidō and Honshū
• Turkish Straits – collectively refers to the Turkish straits the Bosphorus and the Dardanelles between Asia and Europe

V

• Vitiaz Strait – between New Guinea and Long Island

W

• Wantsum Channel – former channel between the Isle of Thanet and the mainland of southern England; now drained, and Thanet now only separated from the mainland by the River Wantsum, a minor drainage channel
• Wetar Strait – between Timor and the Indonesian island of Wetar
• Windward Passage – between Cuba and Hispaniola

Y

• Yucatán Channel – between Mexico and Cuba

 

[Altruist]

Well, I guess, if you are keen on implementing it, go ahead.
But I would severly shy away to ask any Modder to implement such a long list.

PS: Nevertheless, great to have such a linked list available in the forum.

 

[InfArmMot]

Well, far from all straits should be accepted as useful for ship-watching-activities. Some, however, like the Little Belt — between the island Funen and mainland Denmark, accounting for only 800 meters at its minimum width (a maximum of 400 meters observation from each side), should probabæy be acceptable. Or the Strait of Messina — between Sicily and mainland Italy, accounting for only 3.1 kilometers at its minimum width (a maximum of 1550 meters observation from each side), might be acceptable?

I am talking about spotting ships in bad conditions, without infrared. Thus, night, rain, snow, fog or sandstorm.

Perhaps the Strait of Gibraltar was a bad example? Because, those 7000 meters from each side, is in fact quite a bit. Unless the weather is clear and it is daylight.

In terms of the event, I am thinking of an option to invest in a network of coastal intelligence stations. This in minimum two preselected provinces, adjacent to a list of acceptable straits. The provinces must not be on enemy ground and perhaps relations between the host country and your nation, has to be above 100. Maybe there should even be an ideological requirement? So for instance fascist and national-socialists governments, would allow each other to set up stations. However, they would not allow a democratic government to do it, regardless of the level of relations?

But what should such an investment cost? I like the idea of a coastal station network in two technological phases, the first without and the second with infrared equipment.

First event:

INVEST IN SHIP WATCHING ACTIVITIES (network of coastal intelligence stations): 650 money

5% chance of spotting lonely surface vessels in bad weather (night, rain, snow, fog, sandstorm)

10% chance of spotting convoys in bad weather (night, rain, snow, fog, sandstorm)

15% chance of spotting navies in bad weather (night, rain, snow, fog, sandstorm)

90% for all spotting in clear weather, daylight.

Second event:

INVEST IN SHIP WATCHING ACTIVITIES (network of coastal intelligence stations — INFRARED Equipment): 1400 money

55% chance of spotting lonely warships in bad weather (night, rain, snow, fog, sandstorm)

65% chance of spotting convoys in bad weather (night, rain, snow, fog, sandstorm)

75% chance of spotting navies in bad weather (night, rain, snow, fog, sandstorm)

90% for all spotting in clear weather, daylight.

In terms of the maximum width, where you invest in coastal stations in two opposite provinces, what should the acceptable maximum width be?

If we use the video below, as an example of how difficult it is to spot a blacked out surface vessel, in this case the German vessel Blücher at Drøbak Sound, then we can see that at a distance of around 1800 meters, it seems that the Norwegian coastal station, is only able to detect the lonely German warship, with the help of active search lights.

So, a German spy, at the Gibraltar, equipped only with binoculars, will not be able to spot anything passing through the center of the Gibraltar strait, at around 7000 meters. Clearly, here, infrared is needed.

Therefore, the acceptable maximum width, should be under 1800 meters. However, I am not sure how low the width have to be?

 

[ConjurerDragon]

Well, far from all straits should be accepted as useful for ship-watching-activities. Some, however, like the Little Belt — between the island Funen and mainland Denmark, accounting for only 800 meters at its minimum width (a maximum of 400 meters observation from each side), should probabæy be acceptable. Or the Strait of Messina — between Sicily and mainland Italy, accounting for only 3.1 kilometers at its minimum width (a maximum of 1550 meters observation from each side), might be acceptable?

Geographically - sure. But for whom? Spain controlled both sides of Gibraltar and was aware and allowed the german presence and installations due to ideological and pragmatical considerations - for a while. Would Germany need to put agents there - or better fly recon missions over the med for the same purpose?

Regarding the detection chance - I would never give anything a 100% chance to detect something - not even in full daylight and unobstructed view, but 99% at most. After all you just might miss e.g. the Heavy Cruiser that travels through with a battleship on each side. Or like in the battles in the Pacific you might mistake one ships for another - some pilots reported carriers when they actually spotted tankers... Or if you have 3 guys on each side of the strait for 24/7 observation and everyone taking 8 hours watching through a binocular... Everyone has to blink, drink, eat, visit the toilet sometime. If that is supposed to be a covert agent operation we are not talking about dozens of soldiers on foreign soil. And we should make sure to make it an option that is feasible only for places where you can´t operate some air reconnaissance, because flying over a strait with a high resolution camera is far better than trying to spot something from the shore with handheld or even tripod binoculars.

 

[InfArmMot]

Geographically - sure. But for whom? Spain controlled both sides of Gibraltar and was aware and allowed the german presence and installations due to ideological and pragmatical considerations - for a while. Would Germany need to put agents there - or better fly recon missions over the med for the same purpose?

It would be for the nation installing the coastal spotting stations. So in the case of Gibraltar, when both sides are controlled by Franco's Spain, it would be either for Nazi Germany, or Fascist Italy. However, only if the requirements are met. These come in two phases. The first is a diplomatic phase and the second consist of the two investment events, each one being granted when the technological level has been reached and the money are there.

I. THE DIPLOMATIC PHASE

Requirements for Germany to request Spain, to install German stations and German agents in the two provinces; Gibraltar and Tangier, for ship watching activities.

1. The diplomatic relations between the Germany and Spain, should be at least 100.

2. The two nations should run the same or a similar ideology.

3. The host nation is official a neutral country.


II. THE INVESTMENT EVENTS.

First when the requirements of the diplomatic phase has been processed, then the technological level has to be researched. Only hereafter the first of the two investment-events pop up on the players screen, on the left, along with all the other event-options. After this, the money has to be there, in order to launch the event.

These two are as follows:

1. INVEST IN SHIP WATCHING ACTIVITIES (network of coastal intelligence stations): 650 money.

2. INVEST IN SHIP WATCHING ACTIVITIES (network of coastal intelligence stations — INFRARED Equipment): 1400 money.

In terms of technology, it could be a quickly researched technology, under Naval Doctrines, with the title COASTAL SHIP SPOTTING. The requirement to research it would be basic computers.

Regarding the detection chance - I would never give anything a 100% chance to detect something - not even in full daylight and unobstructed view, but 99% at most. After all you just might miss e.g. the Heavy Cruiser that travels through with a battleship on each side. Or like in the battles in the Pacific you might mistake one ships for another - some pilots reported carriers when they actually spotted tankers... Or if you have 3 guys on each side of the strait for 24/7 observation and everyone taking 8 hours watching through a binocular... Everyone has to blink, drink, eat, visit the toilet sometime. If that is supposed to be a covert agent operation we are not talking about dozens of soldiers on foreign soil. And we should make sure to make it an option that is feasible only for places where you can´t operate some air reconnaissance, because flying over a strait with a high resolution camera is far better than trying to spot something from the shore with handheld or even tripod binoculars.

True. And it should probably be 90% at max.

Thanks for asking these questions. Also in terms of counter measures, there should be something the allies could do to stop or obstruct the ship watching activities?

 

[Baron Jukaga]

Not a terrible idea but I'm pretty sure that any further patches will just be bug fixes and polish not new features. I'd like to be proven wrong!

 

[InfArmMot]

Let's hope so, because I have no idea of how to make a small modification like this one. However, what I can do, is to promote the idea and attempt to formulate how it should be implemented in the next patch.

Especially in multiplayer games, this small and realistic modification, will provide different nations with important know how. This, potentially speaking, for:

1. The Baltic Sea at the Danish and Danish/Swedish strait.
2. The Black Sea at Bosporus and the Dardanelles.
3. The Mediterranean sea at Gibraltar and The Suez canal.
4. The Panama canal.
5. The Strait of Messina.

Little Belt - Wikipedia

en.wikipedia.org

Øresund - Wikipedia

en.wikipedia.org

Bosporus - Wikipedia

en.wikipedia.org

Dardanelles - Wikipedia

en.wikipedia.org

Panama Canal - Wikipedia

en.wikipedia.org

Strait of Messina - Wikipedia

en.wikipedia.org