About 14 percent of the 1.4 million troops in the active-duty military are women. About 280,000 women were deployed to Iraq or Afghanistan. About 150 women died in those two conflicts.

Although there may be growing support in the military to opening some jobs in combat units to women, there remains stiff opposition from the infantry, where the physical demands — like walking long distances carrying heavy loads and handling bulky weapons — are most demanding.

In a widely circulated article, a female Marine Corps captain who served in Iraq and Afghanistan wrote in the Marine Corps Gazette this year that seven months in Afghanistan left her physically broken, with muscle atrophy in her leg and an ovarian condition that left her infertile.

“I am confident that should the Marine Corps attempt to fully integrate women into the infantry, we as an institution are going to experience a colossal increase in crippling and career-ending medical conditions for females,” the article’s author, Capt. Katie Petronio, wrote.

But one of the plaintiffs, Capt. Zoe Bedell of the Marine Corps, said Captain Petronio’s experience might be very different from other women’s.

“We all should be able to choose how we pursue our careers and what conditions we want to subject ourselves to,” said Captain Bedell, adding that she left active-duty service because her career had been limited. “We can’t have a policy that says I’m not allowed to compete.”

In 2010, Captain Bedell commanded a “female engagement team” that worked alongside all-male infantry units, helping to gather intelligence from civilians. Her teams “patrolled with men every day, sometimes twice a day,” Captain Bedell said in the news conference. Two senior Army Reserve officers filed a similar suit in Washington in May, asserting that the government violated their constitutional rights by barring them from direct combat roles. But the plaintiffs in the new lawsuit are younger and were all exposed to combat, which, their lawyers believe, may make their case more compelling.

Two of the plaintiffs earned Purple Hearts, including Maj. Mary Jennings Hegar, a helicopter pilot with the Air National Guard who was wounded in 2009 when her medical evacuation helicopter was shot down in Afghanistan. Service Women’s Action Network, an advocacy group, is also a plaintiff in the suit.