Seventeen years ago today, the U.S. and Britain went to war to remove the Taliban from power in Afghanistan. It was morally and politically justified by the Taliban's failure to surrender al Qaeda terrorists responsible for the Sept. 11 attacks. The Western alliance drove the Islamic totalitarians from power swiftly, within weeks.

Yet, we're still there. On Thursday morning, another American serviceman was killed in battle in Afghanistan. Nearly 2,400 Americans have now died in this war, and Afghanistan is still mired in poverty, chaos, and violence.

What are we doing there? Why are we still fighting this war after 17 years?

The three presidents to preside over this war have all failed to focus the mission clearly toward America's real interest, which is to prevent multinational terrorist organizations such as ISIS and al Qaeda from establishing a stronghold.

Instead, we took up the hopeless and endless task of nation-building. Every audit of American efforts to build a safe and stable Afghanistan have showed failure. The waste in money and lives goes on. The problem is not American incompetence or stinginess, but that the big goal has always been unrealistic.

Billions of dollars have been spent on schools, roads, and infrastructure projects in rural areas that remain under the heel of the Taliban. These projects could work only if America ran a police state, requiring hundreds of thousands of soldiers and Marines.

The issue in places such as Helmand is not simply that the Taliban dominate the area and cannot be dislodged, but that the area is a patchwork of fiefdoms run by local tribes with whom we are unable to deal.

The Bush dream that guns, money, and lawyers could build stable democratic societies anywhere on Earth has been tested in the field, and it has failed. In Iraq, where there was some memory of institutions, it has largely failed. In remote parts of Afghanistan, it has failed completely.

Civil society will not soon come to Helmand. But in cities such as Kabul, the capital, civil society is steadily growing stronger. We must learn to live with an Afghanistan that has two faces.

The hubris of the Bush doctrine was deeply unconservative. President Trump has taken a humbler route, directed toward wounding the Taliban to keep it weak, but not pretending to be able to eradicate it entirely. The administration has also finally made Pakistan understand it may not support our enemies in Afghanistan.

America's goals should be to avoid making things worse in Afghanistan, contain the Taliban, and focus more on the Islamic State. These are not lofty goals, but lofty goals have proved to be pipe dreams that produced a 17-year nightmare.