The service members who fought in Afghanistan over the past 20 years can hold their "head up high" for preventing an attack on the U.S. homeland, according to a letter posted Tuesday on the Joint Chiefs of Staff’s Facebook page.

The letter was signed by Army Gen. Mark Milley, its chairman, and U.S. Air Force Chief Master Sgt. Ramón Colón-López. The note addressed the current challenges the military faces after the troop withdrawal from the country, but it largely focused on those who served and "fought tirelessly to defeat violent extremist organizations."

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"To each of you, your service mattered," the letter read. "This is personal for us and we know that this is personal to every one of you."

The letter also addressed the mission to evacuate American citizens and the killings of the 13 service members.

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"This mission was historic and each of you who participated in this operation demonstrated compassion, character, commitment and exceptional competence in the execution of this high risk mission in a very fluid, dynamic, and dangerous operational environment," the letter read.

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President Joe Biden on Tuesday called the U.S. airlift to extract more than 120,000 Americans, Afghans and other allies from Afghanistan to end a 20-year war an "extraordinary success," though more than 100 Americans and thousands of others were left behind.

"I was not going to extend this forever war," Biden declared from the White House. "And I was not going to extend a forever exit."

Earlier this month, former President Bush also issued a statement that recognized the efforts of those who served in the country.

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"Many of you deal with wounds of war, both visible and invisible," the statement read. "And some of your brothers and sisters in arms made the ultimate sacrifice in the war on terror. Each day, we have been humbled by your commitment and your courage. You took out a brutal enemy and denied Al Qaeda a safe haven while building schools, sending supplies, and providing medical care. You kept America safe from further terror attacks, provided two decades of security and opportunity for millions, and made America proud. We thank you from the bottom of our hearts and will always honor your contributions."

The Associated Press contributed to this report