reinforcements

As nouns the difference between reenforcements and reinforcements

is that reenforcements is while reinforcements is .

As nouns the difference between reinforcements and cavalry

is that reinforcements is while cavalry is (military|uncountable) the military arm of service that fights while riding horses.

As nouns the difference between reinforcements and backup

is that reinforcements is while backup is a reserve or substitute.

As a adjective backup is

standby, reserve or extra.