India has threatened before, in other moments of rising tensions, to pull out of the Indus Waters Treaty, which both countries signed in 1960. If India follows through this time, it could restrict the flow of water that is used for most of Pakistan’s crop irrigation and human consumption. Agriculture represents one-fourth of the country’s economy.

India and Pakistan's latest military conflict has expanded, days after India carried out airstrikes in Pakistan that followed an attack by gunmen on tourists in India-controlled Kashmir last month.

Why did India attack Pakistan? Are the two nuclear armed countries at war? US warns Americans to leave areas of conflict. Here's what we know so far.