The U.S. and South Korea launched large-scale springtime military exercises to practice “neutralizing” North Korean nuclear threats on Monday, according to Seoul’s defense ministry.

The first day of the 11-day Freedom Shield exercise saw the allies kick off joint aerial drills at Osan Air Base featuring ROK F-15K fighter jets and U.S. F-16s.

Around 20 assets are participating in the Buddy Squadron Training scheduled to run through Friday, the South Korean air force said in a press release.

“These forces will conduct realistic training such as Defensive Counter Air missions and plan to exchange the latest tactics between the two