New developments in the nuclear powers’ harrowing four-day conflict, along with entrenched religious nationalism on each side, could signal more frequent battles ahead.

NEW DELHI — India and Pakistan agreed to an immediate ceasefire on Saturday, halting days of clashes that killed dozens of people and pushed the nuclear-armed neighbors to the brink of war.

India and Pakistan agreed to an immediate ceasefire on Saturday, unexpectedly halting the worst fighting in decades between the nuclear-armed neighbors, just when their tit-for-tat strikes appeared to be spiraling out of control.