Between now and Inauguration Day 2021, there will undoubtedly be an effort by the Trump administration to lock in as many policy victories as possible through executive action before President-elect Joe Biden takes office. On foreign policy in particular, President Donald Trump has the opportunity to use his remaining time in office to make a lasting, positive impact on our country by closing the door on our two decade-long war in Afghanistan.

Specifically, Trump should issue orders to conduct a full withdrawal of U.S. military forces from Afghanistan by January 20. This would end America’s unnecessary military presence and cement his legacy as the man who ended our nation’s longest war.

Long before he was a candidate for president, Donald Trump strongly criticized the war and advocated withdrawal. As a candidate in 2016, there is credible evidence that his criticism of the war in Afghanistan and other endless wars in the Middle East played a key role in his victory over Hillary Clinton.

Early in his presidency, Trump’s desire to disentangle from Afghanistan was resisted by hawkish advisers such as General H.R. McMaster and Defense Secretary James Mattis. Trump acceded to their demands to stay the course and increase troop levels. Not surprisingly, this “new” strategy — just like every one before it — did not alter the reality that the war against the Taliban could not be won purely through military means.

Instead of muddling along like his predecessors, Trump decided to pursue a different course. In 2018, Trump appointed Ambassador Zalmay Khalizaid as his Special Representative for Afghan Reconciliation and tasked him with starting an intra-Afghan peace process.

In February 2020, Khalizaid’s efforts yielded a historic agreement between the United States and the Taliban that was signed in Doha, Qatar. The Doha agreement created the conditions for peace talks between the Afghan government and the Taliban, while mandating a full withdrawal of U.S. military forces from Afghanistan by May 2021. Since then, U.S. force levels in Afghanistan have dropped to around 4,500 — their lowest level since 2001 — and are currently on track to go to 2,500 by January 2021. Additionally, the Taliban have generally restrained their forces from attacking U.S. personnel and there have been no American deaths from hostile fire since the signing of the Doha agreement.

Unfortunately, Biden indicated during the campaign that he plans to leave forces in Afghanistan. Additionally, Biden appears poised to appoint individuals like Susan Rice, who has been critical of the Doha agreement, to key national security or diplomatic roles in his administration.

Leaving even a small military force in Afghanistan past the May 2021 deadline will almost certainly lead to the loss of more American lives due to the high likelihood that the Taliban will resume attacks against American forces if the U.S. fails to follow the timeline in the Doha agreement. It will also negate the hard work of diplomats and military personnel working under Trump to secure a military exit from Afghanistan that places the future of that country in the hands of Afghans.

That’s why Trump should order the military to complete a full withdrawal from Afghanistan no later than January 20, 2021. During his remaining time in office, he should closely monitor the withdrawal process to ensure it is not undermined by those within the national security establishment who favor a permanent presence in Afghanistan.

This move would have the overwhelming support of the American people. Recent polling shows that over two-thirds of the American public — including military families and veterans — support a full withdrawal from Afghanistan. A full withdrawal would also make it difficult for Biden to re-introduce a large, permanent military presence into the country. Attempting to do so would be logistically challenging and politically difficult due to the likely opposition from progressives that share the Trump movement’s wariness of our endless wars abroad.

We long ago accomplished what we needed to in Afghanistan. Trump has rightly recognized that leaving our troops in place only invites more unnecessary loss of life and does not enhance our security. Completely extricating our military from Afghanistan by January 20, 2021 would prevent the incoming administration from undermining one of Trump’s major accomplishments and cement his legacy as the president who brought an end to our country’s longest war.