Intense nationalism and disputed history — and maps — stoke the neighbors’ hostilities. Even a surge of international diplomacy has brought little hope of a lasting peace.

Cambodia and Thailand agreed to an "immediate and unconditional" ceasefire Monday after five days of intense fighting along their shared border. The ceasefire, negotiated in Malaysia with involvement from the U.S. and China, took effect at midnight.

Tensions along Cambodia's northern border with Thailand have been simmering since May, when a Cambodian soldier was killed in a clash with Thai forces.