The United States and South Korea started their biggest joint military exercises in years Monday amid fears that North Korea is preparing for a new nuclear-weapons test. The massive drills, named Ulchi Freedom Shield, are set to last until Sept. 1 and represent the largest military maneuvers of their kind since 2017. Diplomatic efforts to reduce tensions with Pyongyang and the COVID pandemic led to a scaling back of the exercises in recent years. South Korean President Yoon Suk-yeol promised to “normalize” the joint exercises, which are planned to run on an annual basis, and to bolster deterrence against the threat from Kim Jong Un’s regime. The drills come after Kim’s firebrand sister, Kim Yo Jong, told the South Korean president to “shut his mouth” after he offered to exchange economic aid for denuclearization.