When the United States fought its ill-fated war in Vietnam, it sent men into battle at 18 – as many other nations do today. More ominously, Russia lowered its draft age to 18 this year as part of a drive to potentially recruit hundreds of thousands more soldiers to fight its war in Ukraine. While Ukrainian men between the ages of 18 and 60 must register at military enlistment offices and are not permitted to leave the country under martial law, only those over the age of 27 are eligible for conscription.