sinking of the Lusitania
There was no one main airplane. Each country developed a number of airplanes throughout the war.
The assassination of Ferdinand light the fuse that started World War One
influenza was the main one
AnswerMilitarismAlliance SystemImperialismNationalism
Socialism
Malaria was one of the main ones.
Yes
One of the main things was the Second World War.
Hasburg Empire was one of the greatest ruling families in Europe. The main goal of the Empire in World War I was to contain its national minorities.
The Moroccan Crisis (1905-1906) was the first crises and was one of the long term causes of World War One. The fight over control of Morocco broke down the trust between the major European Powers. The second crisis was the Bosnian Crisis (1908-1909) and was caused by Austria-Hungary's desire to annex Bosnia-Herzegovina. This crisis led to the assassination of Franz Ferdinand which triggered the breakout of the war.
One of his main discoveries was Quantum Electrodynamics. However, sadly one of his main inventions was the atomic bomb during World War II.
There was no one "world leader", but the two main competing nations were the United States and the Soviet Union.