This article originally appeared in History of War magazine issue 149.

Armed clashes on the remote, disputed border between Cambodia and Thailand have killed at least 12 people on Thursday, in a dramatic escalation of tensions that threatens to erupt into a broader conflict.

Long-simmering tensions between Thailand and Cambodia escalated to deadly violence on July 24, setting off five days of military clashes at multiple spots along the roughly 800-kilometer (500 mile) border.