South Korea’s missile defense buildup will depend on whether Seoul can field, replace and coordinate enough interceptors to withstand sustained North Korean attacks while its defense industry works through a growing backlog of foreign orders.

Pyongyang’s growing missile arsenal is making that challenge more urgent. North Korean state media said a hypersonic intermediate-range missile launched Oct. 3 flew in a “wave-like trajectory mode” before striking a target about 620 miles (1,000 kilometers) away in the East Sea.

South Korea’s defense ministry said allied forces tracked the missile from launch and assessed that existing South Korean and U.S. systems could detect