The main opponents of Napoleon was Britain, and later joined by Austrio-Hungary, Germany, the Russian Empire, and many other smaller nations.
These countries felt a need to oppose France under Napoleon, for they themselves had monarch governments, and on seeing the French Revolution that led to the capitulation of the Royal government and civil unrest, which led to the rise of (what they thought) was a fanatical Bonaparte, they believed that, if their own people took a hold of the ways of the French, that they themselves would be thrown out of power. This led to the governments of these other nations to band together to throw Bonaparte out and reinstate the royal family to re-balance the royal structure in Europe.
