In Pride of Nations, you have to maintain your forces each turn.
This is called upkeep, and should you fail to pay your men or spend goods to keep your war materials in good shape, problems will start to appeas, like a loss of cohesion for example. Campaigning will also be costlier to your troops, so if you want to reduce this spending, there is always the option to garrison them (fortress units, a special type of unit that is almost immobile, except by train, is also the cheapest to maintain while powerful in defense).
But there are more resources to spend than just money, as if you needed more! Coal, one of the preeminent resources of the era, will have to be watched over with great care. Coal is used in the game for many things. First, there is the industrial usage. Few of your industries will be able to run without coal, and no industry, no place under the sun either! Then you need coal to move your ships. Not all, as many nations start in 1850 with a significant portion of their fleet powered by sail only. But developed nations were building more and more steam ships, powered by coal furnaces. Warships and merchant fleets will soon all use coal for power, and this will place an even bigger emphasis on the need to maintain a good source of this asset for your country. However, remember that ships that don’t move don’t use coal, so this is ‘intelligent upkeep’ here. We won’t make the game spend your coal for ships that stay in harbor…
This need for sources of coal will also make you build coaling stations around the world, should you have access to some lands free of any other western power. The need to build coaling stations for their ships was one of the motivations to grab colonies for European powers,. Rest assured though, you can also secure supply rights in other countries, so as to be able to use their facilities.
And last but not least, railways. Having a developed rail net is good for your economic power, because productivity will greatly benefit from it. But for each region with a railway, there will be a cost in coal to pay every turn, to represent civilian traffic. That’s not all though, as PON features many special orders for your troops, one being to move by rail. The rail pool you can use depends on the extent of your rail network, and troops moving by rail will also place an extra burden on your coal reserves. Choices will be difficult on how to use coal, but also very interesting to make!