There are many reasons why the First World War happened. The rise of nationalism, excessive love of country, helped to plunge nations into conflict. In any nationalist setting, an act against another nation has to be defended and pursued at all costs. This would mean that war is almost inevitable in such a setting. The rise of militarism means that these nations, under the guise of nationalism, fed and grew their military/ armies to such a level that when war was declared, everyone was ready to fight it. The alliance system, where nations had secret alliances with one another so that if one was threatened, others actually were involved as well, helped make the conflict such a wide ranging and protracted one. The advancement of industrialization which helped many nations produce the instruments and elements needed to fight wars helped to make war another reality, as well.
Nationalism is being a strong supporter of your country's interests.
An alliance is an agreement that is made between two or more countries. When this happens they become allies. If a country was an ally and declared war it meant that you were in on the war as well.
Imperialism is when a country takes another country and makes that country follow their rules. By 1900, the British empire was very big. It extended over five continents. France was in control of a large portion of Africa. This caused a rivalry with Germany.
Militarism means that the military is given a high profile by the government. The European divide led to an arms race. Armies were getting larger and there was a battle for who was in control of the seas. The British introduced the "Dreadnought" which was a large battleship. The Germans followed suit with ships of their own.
Nationalism is when you think that your kind of people is better than everyone else. It helped lead to WWI because people of the same ethnic group (like Slavs) made alliances to oppose other groups.
Imperialism is when your country tries to go and take colonies. This caused competition between countries for colonies.
Militarism is when you glorify and admire the military. You start to think that they know best and that war is good.
Alliances are just deals between countries to help one another. These helped expand the war because for example, when Austria-Hungary declared war on Serbia, Serbia's allies jumped in and that made A-H's allies do the same.
The chief causes of World War I were results of several developments that had their origin in 1800's.These developments included the rise of nationalism, a build-up of military might, competition for colonies, and a system of military alliances.
During the 1800's, a spirit on nationalism swept across the continent that helped bring about the Great War. Nationalism is the belief that loyalty to a person's nation and its political and economic goals comes before any other public loyalty. People who shared a common language, history, or culture. began to view themselves as members of a national group, or nation. This form of patriotism came into conflict with the goals of one or more other nations. Nationalistic pride also caused nations to magnify small disputes into major issues.
Nationalism led to the rise of two new powers - Italy and Germany - formed by union of many small states.On the other hand, nationalism weakened the eastern European empires of Austria-Hungary, Russia, and Ottoman Turkey which had ruled many national groups that clamoured for independence. First Greece and then Montenegro, Serbia, Romania, Bulgaria, and Albania won independence in the period from 1821 to 1913. Each of these state quarrelled with neighbours over boundaries
A build-up of military might occurred among European countries before World War I broke out. By the late 1800's, Germany had the best-trained army in the world. Other European countries also followed Germany's example and expanded their armies.
In 1898, Germany began to develop a naval force to challenge the British navy. Concerned by this, the British navy launched the Dreadnought, a modern battleship that had greater firepower than any other ship of its time. In response Germany also rushed to build ships like that. There were other advances in technology that increased the destructive power of military forces. Machine guns and other new arms fired more accurately and more rapidly than earlier weapons. Steamships and railways could speed the movement of troops and supplies. This made it possible to fight longer wars and bear greater losses than ever before.
During the late 1800's and early 1900's, European nations gained control over nearly all of Africa and much of Asia as their colonies. These countries competed for colonies leading to incidents between rival powers flaring frequently.
A system of military alliances developed in Europe in which countries entered into a military agreement with one or more other countries, which provided that in case of an attack on one country other members of the alliance would come to the country's aid or at least remain neutral. Wile this arrangement provided protection for a country, it also created certain dangers. I made countries more bold in taking risks of war. Also it meant that war between any two countries would automatically get escalated to war between many other countries although some of the countries have no grudge against the countries they are fighting. Further. the terms of many such alliances were kept secret, increasing the possibility of a country might misjudging the consequences of its actions.