In recent years, the United States and South Korea have cancelled some of their regular drills and reduced others to computer simulations, to create space for diplomacy and allay Covid-19 concerns. But after North Korea dismissed South Korean president Yoon Suk Yeol's offer to exchange denuclearisation steps and economic benefits, the USA and South Korea began their biggest combined military training in years on 22 August, heightening their defence posture against the growing North Korean nuclear threat. The Ulchi Freedom Shield exercises, which will continue until 1 September, include aircraft, warships, tanks, and potentially tens of thousands of troops. They could draw anger from Pyongyang, which has pushed its weapons testing activity to a record pace this year while repeatedly threatening conflicts with Seoul and Washington amid a prolonged stalemate in diplomacy. Some say North Korea sees the exercises as rehearsals for an invasion.