South Korea's President Yoon Suk Yeol on Tuesday said he would lift martial law just hours after he imposed it, in a brief and confusing episode in which he blasted the opposition as "anti-state forces" threatening the country's democracy.

The unexpected move from Yoon — the first time martial law has been declared in South Korea in more than four decades — alarmed the United States and the country's other allies.

What do we know about the imposition, its lifting and what might come next?