The causes of the war that was most important was the imperialism. Imperialism made countries relations fracture in competition on who's stronger.
Weapons of the War
The major countries that fought during the war were Britain, France, Russia, Italy, and the United States.There were Central Powers and Allied Powers.The Central power in my opinion had the advantage when the war began.
Effects of the War
Machine guns and poison gas were the newest weapons of the time and the most deadliest . The countries that held these weapons made great advantages in many fights.
Germany were effected greatly which caused their economy to suffer. If it weren't for their continuation of the war, then they wouldn't have suffered.