Japanese forces overran much of Southeast Asia in 1942, seizing Burma from British colonial possession. In order to supply its troops in Burma the Japanese planned a railway line from Thailand (under Japanese control) to replace the long voyage by sea, which was vulnerable to submarine attack. About 60,000 Allied prisoners of war - primarily British, Australian and Dutch - and 180,000 conscripted Thai, Burmese, Tamil, Chinese and Malay labourers were forced into work on the project. About 16,000 POWs and an estimated (the Japanese didn't keep records) 90,000 Asian labourers died for the 258-mile track, earning the Death Railway its nickname.
The bridge that currently spans the river Kwai is not the wooden structure immortalised in Pierre Boulle's book and the subsequent film (which was filmed in Sri Lanka). The wooden bridge was intended only as a temporary measure while the permanent concrete and steel bridge was under construction a few hundred metres upstream. Both bridges were completed in 1943.
The curved sections are original; the square sections replace the parts destroyed by Allied bombing raids in 1945.
Although by the end of the war much of the Thailand-Burma line was in poor condition, part of the railway was relaid by Thai Railways and is still in use. You can take a journey from Nam Tok (Waterfall) station along the original route, including sections of original wooden trestle constructed in terrifyingly hazardous conditions on a sheer cliffside by those POW and civilian labourers.
The route is fantastically scenic, offering beautiful views over the Kwai River, but as you think about the incredible human suffering that went into the construction - clearing a path through dense jungle (and if you've ever seen a bamboo thicket you'll be even more in awe), and working 18 hour shifts cutting gullies into solid rock with dynamite and basic tools - it's a journey laden with emotion.
Although I've visited this POW cemetery (the largest of three in the area to which the remains of thousands of POWs were relocated from their temporary graves along the railway) before, it still knocks me for six. Rows and rows of headstones of thousands of men, almost all aged between 20 and 35, who died so far from home. It makes it all the more sad that they died not fighting for what they believed in, but cruelly worked to death.
Kanchanaburi should be a compulsory stop on any Thailand itinerary.