Say what you like about Afghans, but they’re admirably straightforward. The mobs outside the bases enflamed over the latest Western affront to their exquisitely refined cultural sensitivities couldn’t put it any plainer:

“Die, die, foreigners!”

And foreigners do die. USAF Lieutenant Colonel John Loftis, 44, and Army Major Robert Marchanti II, 48, lost their lives not on some mission out on the far horizon in wild tribal lands in the dead of night but in the offices of the Afghan Interior Ministry. In a “secure room” that required a numerical code to access. Gunned down by an Afghan “intelligence officer.” Who then departed the scene of the crime unimpeded by any of his colleagues.

Some news outlets reported the event as a “security breach.” But what exactly was breached? The murderer was by all accounts an employee of the Afghan government, with legitimate rights of access to the building and its secure room, and “liaising” with his U.S. advisers and “mentors” was part of the job. In Afghanistan, foreigners are dying at the hands of the locals who know them best. The Afghans trained by Westerners, paid by Westerners, and befriended by Westerners are the ones who have the easiest opportunity to kill them. It is sufficiently non-unusual that the Pentagon, as is the wont with bureaucracies, already has a term for it: “green-on-blue incidents,” in which a uniformed Afghan turns his gun on his Western “allies.”

So we have a convenient label for what’s happening; what we don’t have is a strategy to stop it — other than more money, more “hearts and minds” for people who seem notably lacking in both, and more bulk orders of the bestselling book Three Cups of Tea, an Oprahfied heap of drivel extensively exposed as an utter fraud but which a delusional Washington insists on sticking in the kit bag of its Afghan-bound officer class.

Don’t fancy the tea? A U.S. base in southern Afghanistan was recently stricken by food poisoning due to mysteriously high amounts of chlorine in the coffee. As Navy Captain John Kirby explained, “We don’t know if it was deliberate or something in the cleaning process.”

Oh, dear. You could chisel that on the tombstones of any number of expeditionary forces over the centuries: “Afghanistan. It’s something in the cleaning process.”

In the last couple of months, two prominent politicians of different nations visiting their troops on the ground have used the same image to me for Western military bases: crusader forts. Behind the fortifications, a mini-West has been built in a cheerless land: There are Coke machines and Krispy Kreme doughnuts. Safely back within the gates, a man can climb out of the full RoboCop and stop pretending he enjoys three cups of tea with the duplicitous warlords, drug barons, and pederasts who pass for Afghanistan’s ruling class. The visiting Western dignitary is cautiously shuttled through outer and inner perimeters, and reminded that even here there are areas he would be ill-advised to venture unaccompanied, and tries to banish memories of his first tour all those years ago when aides still twittered optimistically about the possibility of a photo op at a girls’ schoolroom in Jalalabad or an Internet start-up in Kabul.

The last crusader fort I visited was Kerak Castle in Jordan a few years ago. It was built in the 1140s, and still impresses today. I doubt there will be any remains of our latter-day fortresses a millennium hence. Six weeks after the last NATO soldier leaves Afghanistan, it will be as if we were never there. Before the election in 2010, the New York Post carried a picture of women registering to vote in Herat, all in identical top-to-toe bright blue burkas, just as they would have looked on September 10, 2001. We came, we saw, we left no trace. America’s longest war will leave nothing behind.

They can breach our security, but we cannot breach theirs — the vast impregnable psychological fortress in which what passes for the Pashtun mind resides. Someone accidentally burned a Koran your pals had already defaced with covert messages? Die, die, foreigners! The president of the United States issues a groveling and characteristically clueless apology for it? Die, die, foreigners! The American friend who has trained you and hired you and paid you has arrived for a meeting? Die, die, foreigners! And those are the Afghans who know us best. To the upcountry village headmen, the fellows descending from the skies in full body armor are as alien as the space invaders were to Americans in the film Independence Day.