At 4:30 a.m. on Sunday, in a daring and highly-coordinated assault, 100 Taliban fighters stormed a small combat outpost in Wanat, Afghanistan, near the Pakistan border. 71 U.S. and Afghan forces were inside the outpost during the attack. Another 100 militants fired from a neighboring village, using houses and even a mosque for cover.
Established just a few days earlier, the outpost's defenses, usually simple dirt walls and barbed wire, were unfinished. Some militants forced their way into the camp, sparking intense, and close-quarter combat.
US troops called in a torrent of air support, from B-1B bombers to unmanned Predator planes. By 12 p.m. on Monday, one in five US soldiers was dead, and one in three wounded, not to mention scores of militants who were killed.
"There was very severe fighting," said NATO spokesman Mark Laity. "It is quite common for them to attack our combat outposts, but this was a larger scale attack than normal."
On a visit to the border region last month, ABC News' Jim Sciutto saw the challenge facing coalition forces. With just a few thousand troops distributed in bases many miles apart, forces are ill-equipped to defend a 600-mile border.
US commanders blame Pakistan for not confronting militants on its side of the border; they say Pakistani's inaction is one reason why attacks on coalition forces have risen sharply in recent months.
"This is a porous border. It's a difficult border to police," said Major General Jeffrey Schloesser. "I just want to make sure at the end of the day that does not become a safe haven for Al Qaeda and for other groups that are attacking across the way."
The US is setting up more outposts like the one in Sunday's attack to block the flow of militants from Pakistan. But militants continue to move freely and coalition forces are still fighting militants who escaped.
American commanders have been calling for months for more forces in Afghanistan. Right now, there are 150,000 troops in Iraq, more than four times as many as in Afghanistan. With violence increasing by the day, any troops withdrawn from Iraq might expect to be sent to Afghanistan.