Battle of Guadalcanal in Pacific - one of the ships that fought in this battle was USS Juneau and onboard were 5 Sullivan brothers. They all enlisted together and wished to fought together on the same ship but tragically, Juno was sank, over 600 sailors were killed including all 5 of Sullivan brothers.When the new hit America, there was a small public uproar. So to ensure families that such an event would never happen again, military put into effect a policy known as the Sole Survival Rule.Brothers serving together had to be split among ships so they cannot all be lost during a single brother. Now, if all other brothers were to die, the last of them would be sent home.

Now, nobody would probably send a suicidal mission behind enemy line to save one private as depicted in Saving Private Ryan.

EDIT: name of the ship from "Juno" to "Juneau"