What led to the construction and use of trenches in combat?

(can someone . has to be turned in 1) - explain one similarity between the federal, state, and local governments. ( question 2)- explain one difference between the federal, state, and local governments. ( question 3)- explain one similarity between the federal executive branch and the state executive branch. ( question 4) - explain one difference between the federal executive branch and the state executive branch. (question 5) - explain one similarity between the federal legislative branch and the state legislative branch. ( question 6) - explain one difference between the federal legislative branch and the state legislative branch. ( question 7) - explain one similarity between the federal judicial branch and the state judicial branch. ( question 8) - explain one difference between the federal judicial branch and the state judicial branch.