The withdrawal of U.S. troops from Afghanistan signals the end of a war that involved close to 800,000 American service members. Defending against new threats will require the U.S. to replenish its all-volunteer force with fresh recruits ¡ª a task made harder by the dwindling number of Americans willing and able to serve.

The U.S. currently has 1.3 million active-duty service members. Due to attrition and retirement, the military needs to find more than 150,000 new recruits every year to meet its overall ¡°end strength¡± goal. In 2020, the Army, Navy, Air Force and Marines all hit their annual recruitment goals ¡ª but those figures were distorted by a historically weak job market, as active-duty service members delayed plans to re-enter the civilian sector, reducing the need for new hires. Last year¡¯s target of 61,200 new Army enlistees, for instance, was 20% lower than in 2018, when the Army failed to meet its goal.

Recruiting isn¡¯t easy. At least 70% of Americans between 17 and 24 are ineligible for military service due to obesity, mental-health issues, past drug use, criminal records or lack of a high school degree. Overall, only 13% of young adults express a positive propensity to serve, with women about half as likely as men to consider enlisting.