When did the idea of Burma-Thai Railway evolve?
Probably following the invasion of French Indo-China.
By mid May 1942 Japan had successfully occupied Burma and had it’s sights on India. Wet weather brought about a four-five month halt – thus allowing Britain to re-organise and re-quip India and giving force to attack Japanese shipping to Burma – the existing route was through the China sea, around the Malay Peninsula and up the Malacca Strait to Rangoon.
Making Bangkok the main shipping terminus would save more than a 1,000 miles and reduce potential loss of shipping from Allied attacks.
A rail link was the answer!
There was an existing railway system from Singapore to Bangkok and from Bangkok to Non Pladuk. In Burma there was a rail link between Rangoon and Ye.
Japan had thousands of POWs to use as a labour force.