In Imperialism: Concert of Europe, nations are able to influence each other with various results. Influence is propagated by placing Influence Tokens on the Nation you wish to influence. What determines the number of influence tokens you have? For each Army unit a Nation possesses, it may place one influence token on a nation that borders your home territory. For each Navy unit you possesse, you may place one influence token on a nation that can be reached overseas (i.e., either it has a port or it borders one of your colonies). Each Dreadnought Unit grants two influence tokens, because Dreadnoughts are bad-ass.
What does influence achieve? This is context sensitive. It depends on what sort of nation is influencing and what kind of nation is being influenced (See the previous Dev Diary on unit types).
The most important use of influence is to gain colonies. Traditional Minor nations, such as Sumetera and Namibia, can be colonized by Modern nations. The first step is to place at least one influence token on the target. Each round, there will be a 1 in 10 chance that an “incident” will happen involving your interests in that nation, and this allows the Modern nation to call a Concert of Europe meeting to request recognition of its claim to colonize the targeted nation. Gaining recognition will require granting recognition of claims made by other Modern powers, but we will go into greater details on that in a future Dev Diary.
Russia is a special case. Russia cannot gain colonies, but it is permitted to annex any traditional minor power with which it shares a land border. This allowed Russia to gradually swallow up Central Asia.
Influence can also be used by Major Modern powers to place Minor Modern powers in the Sphere of Influence. Each round each influence token will have a 1 in 10 chance to result in gaining the targeted nation as a sphere. Once a nation is sphered, there is a cool-off period during which other nations cannot influence it. Nations in your sphere of influence will prioritize trade with you over all other nations and will always join you when you are in a major war.
When influence is placed on a Major Traditional power such as China or Persia by a Major Modern power, the result will be to gain a casus belli to impose Free Trade on that nation.
A final use of influence is to gain a casus belli on a nation to take a province from the target. This is only possible when the influencer already has a claim on the province. Russia, for example, gets a claim on Outer Manchuria and so it can place an influence token on China until an incident happens, then declare war on China.
Imperialism: Concert of Europe 