Boris Johnson Praises Those Who Served in Afghanistan: 'You Should Feel Immense Pride'

British Prime Minister Boris Johnson on Saturday thanked current U.K. soldiers and veterans for their service in Afghanistan over the last two decades, as the last of them left the war-torn country.

Johnson posted a letter to Twitter addressed to the "Armed Forces Community," and said those who served in Afghanistan should "feel immense pride." He added has been "lost in admiration for the heroic efforts of everyone engaged in Op PITTING," the country's military operation to evacuate British nationals, and Afghans from the country.

"There has been nothing like it in speed and scale, certainly in my lifetime," Johnson wrote.

On Saturday, the last flight carrying British troops and diplomats left the Kabul airport, The Guardian reported.

In a video posted to Twitter on Saturday, the British ambassador to Afghanistan, Laurie Bristow, said that nearly 15,000 British nationals, Afghan staff and "others at risk" have been evacuated since the operation began on August 13.

Bristow said about 1,000 military, diplomatic and civilian personnel have been working on Operation PITTING in Kabul. U.S. troops continue to evacuate Americans and Afghans in the days after Afghanistan fell to the Taliban.

The British military first entered Afghanistan 20 years ago, in the wake of the 9/11 terrorist attacks in the U.S.

"Our purpose in Afghanistan was simple—to protect the United Kingdom from harm—and you succeeded in that central mission. In the last 20 years, not a single terrorist attack has been launched from Afghan soil against the UK or any other Western country," the prime minister wrote.

Johnson said the troops' efforts also aided "the people of one of the poorest countries in the world."

"Your achievements can be seen in the homes that have electricity for the first time, the fields that were once strewn with landmines but are now safe for cultivation, and in the schools where 3.6 million girls are gaining an education," the prime minister stated.

Johnson also said that "the events of recent weeks will have been hard for the Armed Forces community to watch unfold."

Two British nationals as well as the child of another British national, were killed in in the attack at the Kabul airport on Thursday, according to the BBC.

The attack also killed 13 U.S. who officials identified on Saturday, and dozens of Afghans.

"Over the last two decades, many thousands of you dedicated years of your lives to service in Afghanistan, often in the most arduous conditions," Johnson said.

"In particular, I realise that this will be an especially difficult time for the friends and loved ones of the 457 service personnel who laid down their lives," he added.