the bolan pass is a passes through the toba kakar range of mountains on the border of pakistan . the russians took the threat of a russian invasion of india via the indus and bolan sections very seriously so in 1837 , a french envoy was brought to karachi to gain strength of the emir , dost mahmud . in february of 1839 , the british troops under sir john keane took 12 , 000 men through the zandt pass and enters zabul .
The British Army crossed the Toba Kakar Range of mountains in 1839.