Here is a brief synopsis of Mughal North Western Frontier Policy.
The policy initiated by Akbar on the north western frontier secured to the Empire Kashmir,Sindh,Baluchistan and Makran.He had aquired Qandahar also and had made such arrangements for its defence that the Shah’s effort at reconquest in 1606 was easily beaten back.
But his successors were not so alert so that the Persians captured it a second time in 1622 and finally in 1649.He had a desire to invade Badakhshan but did not take any hasty steps.ShahJahan possessed neither such restraint nor the imagination to camouflage his defeat by tactfully writing to Nazr Mohammad in Persia.
This could have won for him the respect of the people and could then even flaunt his sense of justice and generosity in foreign lands. But instead he covered himself with shame and ignominy.
In the tribal region also Akbar was more successful than those who followed him.It would thus appear that while Akbar’s policy proved the most successful and beneficial to the empire that of Shahjahan proved the most ruinous and the most expensive.