Tom Bowman

Women in the U.S. military have been flying warplanes for years, and recently began serving in artillery and tank units. But they're still barred from direct ground combat.

Now, for the first time in the course's 35-year history, the Marine Corps is putting the first women through its grueling Infantry Officer Course: 86 days crawling through obstacle courses, lugging heavy machine guns, navigating the woods at night.

Col. Todd Desgrosseilliers, the top trainer at Marine Base Quantico in Virginia, says there's a good reason the course is so tough that 1 in 5 Marines fail.

On this morning 150 years ago, Union and Confederate troops clashed at the crossroads town of Sharpsburg, Md. The Battle of Antietam remains the bloodiest single day in American history.

The battle left 23,000 men killed or wounded in the fields, woods and dirt roads, and it changed the course of the Civil War.

It is called simply the Cornfield, and it was here, in the first light of dawn that Union troops — more than 1,000 — crept toward the Confederate lines. The stalks were at head level and shielded their movements.

Gunmen wearing Afghan police and army uniforms have killed 40 U.S. and NATO troops so far this year, and the top American commander in Afghanistan says there is no single reason — and no simple solution.

Taliban infiltrators, disputes between NATO and Afghan security forces, and even the timing of Ramadan, the Muslim holy month, are all factors, according to Gen. John Allen.

"We think the reasons for these attacks are complex," says Allen, who spoke by video link from Kabul on Thursday. Ten of the American deaths have come in just the past two weeks.

The top officer in the U.S. Air Force, Gen. Norton Schwartz, is stepping down Friday after four years on the job.

Schwartz got the job after his predecessor was fired for — among other things — clashing with his Pentagon bosses over how many fighter jets the military needs.

Schwartz is most likely to be remembered for pushing another kind of aircraft: drones.

At this moment, dozens of these unmanned aircraft are flying high above Afghanistan.

Just don't call them drones when speaking with Schwartz.

"Deathly afraid."

That's what one U.S. official says about the prospect that Syria's vast stockpile of chemical weapons might be used against rebel forces. From a U.S. national security standpoint, an even worse outcome would be for those weapons to fall into the hands of terrorists.

A very small percentage of Americans are now serving in the military — fewer than 1 percent. Some are looking for direction. Others are inspired by a sense of patriotism or by a family member who served in an earlier war. On this Independence Day, we continue with an occasional series, Those Who Serve, a look at the men and women wearing their country's uniform during a time of war.

Capt. Jared Larpenteur is from Cajun Country in Louisiana. His family never expected he'd make the military his career.

(NPR Pentagon correspondent Tom Bowman has been embedded with U.S. troops in Afghanistan this month. On Morning Edition, he reported from the eastern province of Ghazni about what's being called "the last major combat offensive of the Afghan War." Now, he tells us about his interview with the No. 2 U.S. officer in Afghanistan, Lt. Gen. Curtis Scaparrotti.)

Several thousand soldiers from the 82nd Airborne Division are taking part in what is being called the last major combat offensive of the Afghan War.

Their task is to clear Ghazni province in eastern Afghanistan, a Taliban stronghold and a key prize because it straddles the major roads to Kabul and the insurgent supply routes into Pakistan.

But the American troops are challenged by a stubborn enemy and a short time to finish the job.

If there was a place in Afghanistan synonymous with the Taliban, it was the district of Marjah in Afghanistan's southern province of Helmand.

Two years ago, thousands of U.S. Marines and British and Afghan forces descended on this checkerboard of villages, canals and fields. They pushed out the insurgents — but at a heavy cost.

Now, with U.S. combat forces on track to depart in the coming months, many are asking whether Marjah's relative peace will last after the Marines are gone.

'We Have Good Security Here'

Inside a plywood shack at a combat outpost in Marjah, in Afghanistan's Helmand province, three Marines sit before a bank of computers provided by the military to help keep up morale. The dingy outpost is made up of a collection of tents where troops live among swarms of flies and the constant hum of generators.