The first U.S. troops to deploy after the Sept. 11 attacks are suffering from radiation exposure that the government has yet to officially recognize 23 years later. They are a final group of 9/11 service members that comedian Jon Stewart, a champion for first responders, can’t leave behind.

Special operations forces were sent to a former Soviet base in Uzbekistan in early October 2001, where they launched the first missions against the Taliban in Afghanistan, including the secret horseback operation depicted in the movie “12 Strong.” Over the next four years, more than 15,000 U.S. troops deployed to Karshi-Khanabad, known as K2.

Troops found clumps of yellow powder scattered near bunkers where Soviet troops had stored missiles. Testing showed it was radioactive uranium, according to a declassified November 2001 Defense Department assessment.