The First World War was expected to be short, with a quick triumph on either side. On the contrary, the war caused a giant massacre to all the countries involved, and lasted for four years. Also against the expectations of political leaders and military commanders new techniques of fighting were used, as well as new weapons (for example the chloric gas, tanks and aircraft ). Due to all this, 13 million people were killed, of which 2 million were Germans, 1.75 million Russians, 1.5 million Frenchmen, 1 million British and 0.5 million Italians. But death was just one of the worst consequences of the First World War. Just military failures on the fronts, along with other problems directly affected internal politics in a great way. This horrible catastrophe also left most of the countries in huge debts, especially Germany, Austria, Hungary, Russia, and many others. This led to poverty and chaos, and the people were suffering. That is why they started to revolt, but the political system was so exhausted after the war that it didn't do anything to solve this.
The effects of the war sped up the changes. It is an arguable fact, whether the war also had a liberating effect. If it did, it was greatly affected by the downfall of three empires, the Austro-Hungarian Empire, Tsarist Russia and Keiser's Germany. In Russia the tsar abdicated and was replaced by the Provisional Government, but it only took 8 months and Russia moved from autocracy to communism.
It is true that this downfall separated and freed different ethnic groups like Czechs and Slovaks, Serbs, etc. who had been a part of the Austro-Hungarian Empire, because these ethnic groups did get their independent states with democratic constitutions. Land was taken from the aristocrats and distributed to the peasants. The workmen got better conditions to work in, for example bigger salaries, less working time, social securities and so on. Women received the same rights as men, like freedom of speech and the right to vote.
One of the reasons why the democratic development was not very stable was the disagreement of the countries that lost the war, like Germany, Hungary and Austria, because the conditions they were given by the triumphant states were very harsh.
A problem that emerged after the First World War was, that the victorious countries took advantage of the peace treaties. The Treaty of Versailles, which was signed on the 28th of June 1919, confirmed that Germany was responsible for the World War. By signing this Germany had to give up a lot of territory won during the war, had to demilitarise and pay for all the damage caused by the war. Altogether Germany lost 13% of her area, 12% of her population, 16% of her coal, 48% of her iron, 15% of her agricultural land and 10% of her manufactures. The coal and iron lost was because the treaty also gave France the right to coal-mine in the Saar region.
The Secret Treaty of London, signed in 1915, in which Italy was promised land for joining the Entente Powers, though Italy never received it. The Treaty of St.Germain and Trianon dealt with Austria-Hungary, the Treaty of Brest-Litovsk between Russia and Germany, which promised Russia back the land lost during the war. This treaty was cancelled though, and no other effort was put into making up for that treaty somehow. The whole settling of these treaties involved the greatest territorial transformation in the whole European...