The first World War was the most devastating war ever fought in human history. This war started in 1914 CE and lasted for four years three months and 11 days. 

The main reasons of this war are the following :

1. Fierce Nationality : The spirit of nationalism was the soul of the French Revolution. The integration of Germany and Italy was the result of nationalism. But at the end of the 19th Century, this feeling of nationalism took a radical look. France wanted to gain independence, so the Poles, Czechs, Serbs, Bulgarians, etc. inspired by the spirit of nationality, wanted to be independent from Austro-German Emperor. France was looking for opportunities to take revenge from Germany. The solution to this problem would have come out of war. 

2. Imperialist Rivalry between England and Germany : Late 19th Century Germany made rapid economic and industrial progress and left England and France behind in industrial innovation. British made a big warship imperator. Germany also built a rail line linking Berlin to Baghdad by constructing the Nile canal. In this way, it was easier to send troops or goods from Germany in the region. This threatened British colonists. 

3. Rivalry between Germany and France : Germany defeated France in the war of 1871. France had to give their two provinces and industrial areas to Germany. In the year 1904, France and Britain made a secret treaty, according to which France, Morocco and Britain got exemption from arbitrage in Egypt.

4. Creation of Groups : In 1882 set up in Germany, Austria and Italy established that if the war with the allied power is fought, then their military will help. England, Russia and France formed a three-nation treaty in 1907. The formation of the conflicting factions divided the world into two camps. Each group promoted war. 

5. Serbo-Slav movement and Balkan Politics : Eastern region of Europe was known as the Balkans. Many states located in this area, such as Greece, Romania, Bulgaria, Serbia, Montenegro and many other small states were under the rule of the Ottoman Empire. Ottoman began to be powerless in the early 20th Century. The slavs, living in Austria and Russia, launched a national movement in support of Russia which is called the All-Slavic movement, whose independence was to liberate the state of Serbia, the Slavic region. Austria protested this movement. In 1908 Austria and Serbia became enemies of one another. 

6. Diplomatic Treaties : The integration of Italy in Europe and integration of Germany started an era which was the era of secret treaties. France also developed a ‘trination’ friendship with Russia and England in relation to its security concerns. This alliance continued to strengthen until 1914.

7. Mercantile and Colonial Rivalry : Fast industrial development began in England, France, Germany, Italy, Japan and America until the 19th Century. With this raw materials were supplied and new markets were needed for finished goods. England and France received the highest colonial territory in this rivalry. Germany was back in this after 1890 and started efforts to acquire Colonies. Whereby, England and France became their foes and Italy was also looking for new Colonies. 

8. Role of Newspapers : When Britain’s newspapers criticized the policy of German Emperor, William-II in Britain, the people of Germany began to consider England as their enemy. In the same way German newspapers provoked the people of England. Serbian and Austrian newspapers published hard hitting articles against each other about the murder of Ferdinand. It was natural for it to foment anger in both the countries. The situation of war could have been handled only when there was no control over the freedom of press. 

9. International Anarchy : Russian-Japanese war of 1904-05, conflict between France and Germany, Annexation of Bosnia-Herzegovina by Austria in 1908-09 CE and Balkan war, etc. promoted international anarchy. As a result the race of militarism and armament speeded up.

10. Immediate cause : The immediate cause of the first world war was the Austrian invasion on 28 July 1914 CE. Along with this the war started between the major European powers.