The United States has been at war in Afghanistan for 13 years. That is as long as it was at war in the Civil War, the Spanish-American War, World Wars I and II and the Korean War combined. The conflict reflects purposeless inertia in Washington. Keeping nearly 10,000 American troops in Afghanistan would just sustain the bloody status quo.

Then-President George W. Bush was right to oust the Taliban in 2001. Washington had to teach the unmistakable lesson that no government would remain in power if it hosted terrorists who attacked America. But then the Bush administration lost interest, preferring to use terrorism as an excuse to oust Iraqi President Saddam Hussein rather than use it as a reason to rebuild Afghanistan.

Thirteen years later the U.S. and its allies have built a large government bureaucracy and security force, but on foundations of sand. The Afghan government is noted for venality, incompetence and corruption; the military’s performance is uneven at best. Indeed, despite high international expectations and intense outside pressure, Afghanistan could not even hold a fair and free election. The power-sharing agreement between President Ashraf Ghani Ahmadzai and “Chief Executive” Abdullah Abdullah will require extraordinary statesmanship to succeed — a virtue never in high supply in Kabul.

Yet the administration wants to retain 9,800 Americans and roughly 2,000 to 3,000 Europeans in the middle of this mess. President Barack Obama proclaimed a “historic day” with the signing of the bilateral security agreement, reflective of “an enduring partnership that strengthens Afghan sovereignty, stability, unity and prosperity and that contributes to our shared goal of defeating al-Qaida and its extremist affiliates.”

He’s wrong on all counts. The influx of Western cash has created wealth for the elite but not genuine prosperity. Afghanistan’s sovereignty will suffer as long as the government is dependent on foreign forces. Domestic unity has been a mirage for a long time.

Al-Qaida has been ejected from Afghanistan, which is why Osama bin Laden was located in Pakistan. With al-Qaida affiliates active in Pakistan, Syria and Yemen, Afghanistan no longer even counts as a minor front in the war on terrorism.

Finally, the continuing U.S. presence seems unlikely to lead to anything approaching stability. Even these diminished troop levels are to be cut in half by 2016 and reduced to a normal embassy contingent by the end of 2017. The Afghan tragedy goes back decades. Washington has devoted tens of thousands of troops, thousands of lives, tens of billions of dollars and scores of high-level diplomatic missions to fixing the country. Retaining a handful of troops — not enough to defend the government from the Taliban but too many to remain uninvolved — won’t remedy the system’s deep deficiencies.

Ultimately the Afghan people must decide how to live together. That isn’t likely to result in a strong central government — especially one based on liberal, democratic Western ideals. However, what emerges won’t be critical to the United States so long as Afghanistan does not host terrorists bent on striking the U.S. Of course, the ongoing conflict destabilizes Pakistan, but that has been the case for years. Indeed, the United States’ involvement results in frequent confrontations between Washington and Islamabad. A full U.S. withdrawal would reduce conflict. Some analysts fear that India, Iran and Russia might intervene absent a robust American presence. However, “the Great Game” inevitably will be played as Washington’s force levels and interest drop.

Anyway, the most important question for Washington is stability for whom? American security is not dependent on Central Asian stability. No doubt, Washington desires to preserve an intelligence presence in Afghanistan. However, that does not require thousands of military personnel authorized, as under the new agreement, to engage in combat if “mutually agreed.” Naturally, the U.S. hopes to forestall a Taliban victory. But one is not preordained. Taliban brutality and misrule have cost the movement support; the end of foreign intervention would undercut its claims to self rule.

Other factions might prove more resilient than expected. After the Soviets withdrew from Afghanistan their client, Mohammad Najibullah, survived more than three years against the mujahedeen. The U.S. should give up trying to impose stability. The U.S. has discovered time and again — in Iraq, the Balkans, Yemen, Somalia and Libya as well as in Afghanistan — that bombing, invading and occupying other nations rarely delivers stability. Instead, intervention results in new forms of instability.

Two years ago Vice President Joe Biden stated, “We are leaving. We are leaving in 2014. Period.” Unfortunately, that’s another promise the administration intends to break. Never mind the new government in Kabul. U.S. troops should leave Afghanistan. Period.