How far could a Soviet invasion of British India get?

How far could Soviet forces advance in a northern invasion of British India as war began in Europe?

The invasion is expected to stall in Afghanistan, perhaps around Kabul if it reaches that far. Poor transport and supply make both the Afghan route and an alternative through Nepal unattractive.

The proposed invasion is judged first by whether its forces could reach India and remain supplied. Afghanistan's infrastructure is considered inadequate to sustain the advance, with the likely stopping point placed somewhere around Kabul or earlier. The Japanese invasion of India provides the comparison: forces at the end of a supply line encounter a dug-in Indian Army supported by effective logistics, with the Chindits also mentioned. A route through Nepal is considered as a wargame possibility using railways and roads, but the mountain fighting makes it another poor prospect. Soviet operations in Afghanistan faced serious logistical trouble even in the 1970s and 1980s, with airlift and more developed Central Asian infrastructure. Control of Himalayan passes is a further obstacle because local powers can charge for passage or resist an army trying to force its way through. The scenario's exact year remains uncertain.