India and Pakistan engaged in the most intense fighting in decades with four days of escalating conflict that included fighter jets, missiles and drones packed with explosives. It ended almost as abruptly as it began.

India says its strikes into Pakistan-administered Kashmir and Pakistan on Wednesday killed more than 100 militants.

In such a scenario, where Pakistan faces an existential threat, or believes that its territory is about to be overrun, it may decide to “go nuclear”—even at the risk of self-destruction. The latest test of this pattern arose in the aftermath of a terrorist attack in Indian-Administered Kashmir on April 22.

The military operations chiefs of India and Pakistan spoke by phone on Monday, the Indian army said, as New Delhi reopened airports and shares rose in both countries following a ceasefire that paused days of intense fighting last week.

India says its strikes into Pakistan-controlled Kashmir and Pakistan on Wednesday killed more than 100 militants.