“We are a nuclear power, and know how to defend ourselves.”
-Sartaj Aziz, National Security Advisor, Pakistan
Why did Pakistan attack India in 1965 and 1971? In both cases it was preemptive strike by Pakistan, as they felt that India will anyway attack them, so better attack them before they attack us. This phenomenon is called as Hobbesian Trap (named after British philosopher Thomas Hobbs).
It gives explanation for why some countries go for preemptive strike. There is total lack of trust between two countries, so they are always afraid of getting invaded by other country. As a result they also keep increasing size of armed forces, get more and more weapons etc.
Thomas Schelling applied this to game theory. He gives example of armed burglar and armed house owner, when they face each other. Neither of them wants to shoot ex. burglar want to use gun as a threat to allow him to rob, while house owner uses gun to threaten burglar. But when face to face both are afraid of other person shooting first, so are forced to fire as a preemptive strike.
Hobbesian trap can be got rid of by increasing trust and cooperation. If both India and Pakistan get rid of Hobbesian Trap, it will drastically reduce defence expenditure and that amount can be used for welfare of citizens.