The first world war was before founding Konoha. It was the second war where Hiruzen became the Hokage.1st War-He was with the 2nd Hokage and then he became the 3rd
2nd War-I don't really know
3rd War-In the Kakashi Gaiden he gave team Minato the mission to destroy the kanabi bridge in Kusagakure
no it wasn't because tobirama was already hokagethe first world war was before founding konoha. It was the second war where hiruzen became the hokage.