Why can’t the US learn from its foreign policy failures?

AFTER MORE THAN 17 years of the United States pouring blood and treasure into the effort to build an Afghan army and government, why is it that the Kabul government continues to lose ground against the Taliban? Further, why were we unsuccessful creating an Iraqi army that could stand on its own against the Islamic State?

Before that, of course, came Vietnam.

Nor was that the start of the failure of American-backed armies. I was a teenager in 1949 when Chiang Kai-shek’s American-backed Nationalist army lost to the Communist forces of Mao Zedong in China. The American secretary of state, Dean Acheson, having conducted a study on why our side lost, declared: “The Nationalist armies did not have to be defeated; they disintegrated. History has proved again and again that a regime without faith in itself, and an army without morale, cannot survive the test of battle.”

Forty-four years ago, the American-trained and American-supplied army of South Vietnam simply melted away before the less-well-equipped but better-motivated army of North Vietnam. In 1975, I watched South Vietnamese soldiers taking off their uniforms and running away in their underwear as the North Vietnamese closed in on Saigon.

Five years ago, the world watched another American-trained and American-equipped Iraqi army bolt and run when the better motivated Islamic State forces overran Mosul in Northern Iraq.

Why, over and over again, does the side America has backed in these civil wars end up defeated? Four threads connect these lost wars of the last 70 years: corruption, patriotic nationalism, a misplaced belief in American exceptionalism, and self-deception.

I saw corruption on a grand scale in Saigon. Generals and government officials were funneling America’s tax dollars into bank accounts abroad, fielding ghost armies in which there were fewer soldiers on the ground than on the official payrolls. In Baghdad during the American occupation, I learned that billions of American taxpayer dollars were bleeding out to the Persian Gulf and Jordan, causing a laundered money real estate boom in the Jordanian capital. In Afghanistan I learned that Afghan officers and soldiers routinely robbed the villages they were sent to protect. Corruption sapped the people’s belief in their US-backed government in all four wars. Soldiers saw no reason to die for corrupt officials.

A second thread is that our side always appeared to be fighting on the side of foreigners, while the Communists in China and Vietnam, as well as the insurgents in Iraq and Afghanistan, always had a better grip on patriotic nationalism and resistance to foreigners. The anti-colonial struggle was more important than the threat of Communism in most of the post-World War II world, and the Islamist insurgents in Iraq and Afghanistan knew how to exploit the traditional resistance to foreign rule. The Taliban could appeal to patriotism while trying to expel the infidel forces of the United States, just as their fathers, grandfathers, and great grandfathers had resisted the Russians and the British before that in the name of jihad.

A third thread is a curiously American trait of willfully ignoring other people’s history and cultures. I remember asking an American officer in Vietnam if he had read anything of the French experience in Vietnam. His answer: “No, why should I? They lost, didn’t they?” Robert McNamara, defense secretary and an architect of our Vietnam War, said in later life that Americans had never understood the Vietnamese. There were plenty of people who could have helped him understand, but he wasn’t interested. We were Americans — exceptional, and therefore not susceptible to the same forces that thwarted other efforts.

I met Americans in the Green Zone in Baghdad who knew nothing about the great schism between Sunnis and Shia Muslims that was tearing the country apart. American-style democracy was the answer to all ills, they felt. In Afghanistan I met Americans who thought purple ink on the fingers of Afghans who had voted was the answer to a thousand years of tribal and ethnic rivalries.

The fourth thread is self-deception. In Saigon, in Baghdad, and in Kabul I attended briefings in which progress was always being made, the trend lines were always favorable, and we were always winning wars we were actually losing. Wishful thinking is no substitute for reality. Americans can train and assist the armies of those whom we want to support in the civil wars of others, but we cannot supply the motivation and morale that is necessary to survive the test of battle.

H.D.S. Greenway is a former editor of the Globe editorial page.