South Korean President Yoon Suk-yeol heads to Washington on Monday, as the allies bolster military cooperation — including with U.S. regional partner Japan — over North Korea's expanding nuclear weapons program.
Pyongyang has conducted another record-breaking string of sanctions-defying launches this year, including test-firing the country's first solid-fuel ballistic missile this month — a key technical breakthrough for Kim Jong Un's military.
In response, Yoon has pulled South Korea closer to long-standing ally Washington, and even sought to bury the hatchet with former colonial power Japan in a bid to contain North Korea.