Capt. Kristen Griest, at right, participates in an obstacle course at the U.S. Army Ranger School in Fort Benning, Georgia.

Until this week, there was one very important requirement for becoming an Army Ranger: You had to be a man.

On Friday, Captain Kristen Griest and First Lieutenant Shaye Haver became the first women to earn the coveted black-and-yellow tab when they graduated from the U.S. Army Ranger School alongside 94 male soldiers.

Griest and Haver’s graduation is the latest in a series of firsts for women in the U.S. military. In January 2013, the Defense Department opened to women thousands of military jobs that were previously only available to men. Six months later, the Pentagon announced it would allow women in front-line combat roles by 2016. And two days ago, the Navy’s top admiral said “there is no reason” why women cannot train to become Navy SEALs.

Critics of allowing women into Ranger training have said the Army is lowering its standards. But Army spokespeople have said repeatedly that Griest and Haver were subject to the same requirements as their male peers.

“No woman that I know wanted to go to Ranger School if they change the standards, because then it degrades what the tab means,” Griest told reporters Thursday.

So, what does the tab mean? Ranger School has been described as the most physically and mentally demanding program in the Army. Students are required to train for grueling combat operations on minimal food and sleep. Just 45 percent will successfully complete the nine-week program.