There were a number of "casus belli" (Latin for "Causes of War"), but the ultimate reasons were based on Germany's policy of unrestricted submarine warfare.
The "Zimmerman telegram", a German diplomatic message addressed to Mexico, had proposed that Germany and Mexico should enter into an alliance in which previously Mexican territories such as Texas, New Mexico and Arizona would be restored to Mexico when Germany won the war. Mexico ignored the proposal, but the message was intercepted and decrypted by the British, who used it encourage the US to enter the war overtly on the side of Britain. This provided the final impetus for Congress to declare war.
The US did enter World War 1, though not till 1917.
Ultimately gravity overcomes all other forces.
The ozone hole in 1970's was a big one. It caused most to the UV to enter.
Hitler was not in world war one, he was the leader of the Germans in world war two.
Congress and the president also a lot of Americans wanted us to enter world war one
do you mean what caused us entry into world war one? if so then the sinking of the USS Lusitania by German u-boats was what caused American entry into the war
The sinking of the Lusitania was a big one.
The beginning of the cease fire of World War One was all thanks to the Armistice of Compiégne.
The biggest earthquake in the world was the one in India, which was caused by a volcanic erruption.
the flamer caused over 300 deaths in world war one
Great Britain entered WWI because of the idea of collective security, where an attack on one country means an attack on all other countries in the alliance. Therefore, when Germany invaded Belgium, G.B declared war on Germany.
the alliance system caused world war one fear because if one nation caused war with a country that meant that the whole alliance was at war too. It caused suspision because suspicion with countries because some countries believed that there were secret agreements that existed between countries.