It was the beginning of the year 1244, when 60,000 Mongol and Hungarian troops crossed the Danube. The Orthodox defenders on the Danube had panicked and retreated into the major cities of Sofia, Thessaloniki, and of course, Constantinople. Manuel II believed that the Mongols would be wiped out in the Balkans. The Orthodox had forces in excess of 100,000. But suddenly, the Mongols were joined in their trek across the Danube by 20,000 additional Hungarians and other non-Orthodox Balkan peoples.
The 80,000 Mongols went on to lay siege on Sofia, the capital of the Imperial Province of Bulgaria. Further north, the lands of Croatia and Serbia fell to the few Mongols that invaded those areas, since they had been disconnected from the main part of the Orthodox Empire. The 20,000 defenders of Sofia knew that the city would fall. They only tried to hold out for as long as possible to give Constantinople time to prepare itself. They killed about 5,000 Mongols. Eventually, by the end of spring, Sofia fell to the Mongols. Constantinople lay open to the wrath of 75,000 Mongols.
Fighting outside the city of Sofia
The Mongols arrived at the gates of Constantinople on May 29th 1244. Immediately, they began to bombard the city with all their siege weapons. Wave upon wave of flaming rocks smashed up against the mighty walls of Constantinople for days. But still, the thick, giant walls stood firm and showed little damage. For the entire month of June, the Mongols made no direct assault on the city, except for the occasional barrage of rocks.
Then, during the month of July, the Mongols constantly assaulted the city. But Constantinople had recently been hoarded with over 50,000 defenders, which meant it had more defenders than all of Greece. So they easily repelled the Mongols. During the failed July assaults, the Mongols lost over 10,000 men.
Then during the month of August, the Mongols received new energy and renewed their assaults on the city. They concentrated their 65,000 men on one portion of the walls and unleashed all their power, both men and siege engines. The charging men, battering rams, and catapults were too much. So on August 12th, the Mongols crashed through the gates of Constantinople and poured into the city. The populace went into a panic and retreated towards the innermost part of the city. This hampered military movements further and allowed the Mongols to move deeper into the city, massacring and rampaging as they went. By nightfall, half of Constantinople was in Mongol hands, with the exception of Blachernae Palace, which was holding out, although it was deep in Mongol held land. To make the situation even more critical, the entire Imperial Family, including Emperor Manuel II, were trapped inside it, with the 1,000 man Varangian Guard. It seemed as if the now flaming city might fall.
Mongols at the walls of Constantinople, watching the red sky
But then, on the morning of August 20th, 10,000 men from Greece appeared on the horizon. Most were on horseback, and it seemed that they were led by the entire nobility of Greece. They had organized themselves into an army and come to save the Empire! This would go down in history as the greatest show of loyalty in the Orthodox Empire. They charged over the horizon and smashed into the Mongol camp outside the city. Immediately after, they headed straight for Blachernae Palace, where the Emperor and the Varangians were still struggling to hold out.
The charge that saved Constantinople and the Orthodox Empire
They crashed into the Mongols attacking the palace and with the help of Manuel II and his guards; they massacred the shocked Mongol troops. They broke out from the palace grounds and pushed forward, killing every Mongol in their way. Meanwhile an Orthodox pincer movement in the Mongol center trapped thousands of Mongols and allowed the Orthodox to cut them all down. All the Orthodox forces banded together and marched throughout the city, killing every Mongol in sight, until the Mongols were running out of the city. By dusk, the city was in Orthodox hands once more. The Mongols had gone from 75,000 men to 25,000. The Orthodox were not immune to casualties and had lost 30,000 men. But the price was worth it, the Empire was saved!
A diagram of the Siege of Constantinople, following the charge of the Greek nobility