The mountains of northern Iraq have for years been a sanctuary for Kurdish militants fighting a decades-long insurgency against the government in neighboring Turkey.

The group, the P.K.K., made its declaration days after its long-imprisoned leader urged the movement to disarm and disband, but there are still many questions about the prospects for ending 40 years of deadly conflict.

Militants from the Kurdistan Workers' Party have declared a ceasefire, in what may represent a significant political breakthrough for Turkish President Recep Tayyip Erdoğan.