The National Resource Defense Council calculated the consequences of a nuclear conflict between India and Pakistan, first assuming a small exchange of air-burst weapons, and then assuming a larger exchange of ground-burst weapons, which would generate much more fallout:
NRDC calculated that 22.1 million people in India and Pakistan would be exposed to lethal radiation doses of 600 rem or more in the first two days after the attack. Another 8 million people would receive a radiation dose of 100 to 600 rem, causing severe radiation sickness and potentially death, especially for the very young, old or infirm. NRDC calculates that as many as 30 million people would be threatened by the fallout from the attack, roughly divided between the two countries.
Besides fallout, blast and fire would cause substantial destruction within roughly a mile-and-a-half of the bomb craters. NRDC estimates that 8.1 million people live within this radius of destruction.
Most Indians (99 percent of the population) and Pakistanis (93 percent of the population) would survive the second scenario. Their respective military forces would be still be intact to continue and even escalate the conflict.
A couple dozen small nukes may kill millions, but they don’t constitute Mutual Assured Destruction — which would be scary, but stable.
(Hat tip to Anatoly Karlin, who emphasizes that nuclear war is not necessarily a true Doomsday event.)