help with #1,2, and 3.
Will mark brainleast if the answer is correct

#1. how did alliance systems help bring about war?
#2. How did trench warfare make offensives long and deadly?
#3. How did the alliance system help bring about war?

#1 / #3

The alliance system caused the World War I to escalate from a regional conflict into a global war. Two major alliances existed in Europe prior to World War I. Austria and Serbia were allied with Germany and Russia respectively, leading Germany and Russia to declare war on each other.

#2

Trench warfare made offensives long and deadly by the nature of it. First, soldiers shelled the enemy trenches day after day. Second, some soldiers charged to attack the enemy, and sometimes, they made it. Trench foot, trench fever, dysentery, and cholera could inflict casualties as readily as any enemy. Rats, flies, and lice were also commonplace.