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.

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.

New Delhi will have to work through a set of unexpected challenges that have emerged consequent to the punitive expedition that was undertaken after the Pahalgam terror attack, which had Pakistan’s fingerprints all over it.