Protestors demanded the passage of the 26th amendment partly because of what event

The Vietnam War! The people demanded a change in the voting age because of the Vietnam War. The US government was drafting 18 year old men to fight, and in the war, but before 1971, some 18 year olds in the US did not have the right to vote. After the US passed the 26th Amendment, all states had to allow 18 year old citizens to vote.