The Chindwin River separated the Japanese and Allies for most of 1943. It was crossed by the Chindits in early 1943 as they headed east to the Japanese rear areas. Then in March 1944 it was crossed west as the Japanese attacked Imphal. In late 1944 it was crossed again eastwards as Slim’s 14th Army reinvaded Burma. Each crossing involved more engineering effort than the last.
In March the river varies from 50 meters wide where it flows fast, to 500 meters across and where it is more or less a lake with no flow. There are lots of points where you could wade across most of it; but crucially never all of it. There are no reliable fords from one side to other because the sands shift too often. You often see people standing in the middle of the river and bigger boats feeling their way forward in 4 feet of water.
The Japanese made a right mess of the crossings with the those in the north in 31 Division being the most problematic. Many drowned and much equipment was lost which is odd since the Japanese were used to crossing rivers although they had much respect for Allied engineering capability which they lacked. However, river crossings have an unforgiving reality to them which no amount of determination, panache or bravery can overcome. Heavy stuff sinks; bushido does not help. Also, on water people tend to all get into trouble at the same time as waves or currents affect all those present and panic spreads. The line between order and chaos is thin.
Is the Chindwin a major obstacle or not? Mutaguchi thought it was not. I think it all depends of the size of the force. A group of 900 odd Chindits would and did find places to cross with some ease providing it was in March. Later as the river rises it would be much harder. It was the Chindit crossings and his own observations which led Mutaguchi to think it was not an obstacle worthy of a defensive line and could presumably be recrossed easily enough.
But as soon as you need to get anything other than a few mules and some hardy infantry across, you need a bridge. The width of the river means that a hasty assault bridge needs to float which means pontoons. The Chindwin offers a classic choice; shorter bridge with lots of current or longer bridge with less. Of course roads access, from each bank might make the choice for you as there is no point having a bridge no one can get to. 300 meter wide pontoons are hard to control in even light currents and the rate of crossing such bridges is slow. The good news is the Chindwin banks are easy to access, being most sandy and sloping, so getting in and out is not too hard. It is notable that when Slim crossed back again in late 1944, the crossing was a big event with lots of engineering support.
In early 1944, I suspect the Japanese thought they could cross the Chindwin like Chindits whereas they were actually much a bigger force. The Japanese force included 20,000 to 30,000 cattle herded by fighting soldiers who did not know how to control the beasts. In any case cattle hate walking and are not that biddable. Burmese cattle seem to like to wallow in water but rarely swim. All cattle in Burma like the afternoon off so even those that do work are not worked after midday. I wonder if Mutaguchi knew this. This whole aspect of Mutaguchi’s plan was, surely, the height of hubris.
The Japanese also lacked air cover and consequently had to cross the Chindwin at night and broke their pontoon bridges to hide them from the RAF during the day. It was probably their exaggerated belief in the capabilities of the Japanese soldier led to short cuts and attempts to wade across which is nearly possible; but not quite. This in turn led to scenes of biblical destruction on some of the crossings which I will describe in the book. At Homalin the Allies, using patrols, managed to destroy 50% of the ammunition heading to Kohima. So you have to feel for the Japanese divisional staff trying to control the crossings. They clearly under estimated the task.
The Japanese in 1943.
My route north took me through Mutaguchi’s area of responsibility in 1943 on the east of the Chindwin. The area is probably now more open but it seems perfect for guerrilla and Chindits operations. There are large open cultivated areas bounded with jungle to hide in. Maj Gen Yamamoto wrote a scathing account of life there in 1943; no food, not much to do, hard to get around. etc. And of course they had to chase elusive Chindits who seemed to go wherever they pleased. I quite see how unattractive it was for the Japanese to simply wait there for the inevitable Allied attack. It was not the idea to attack Imphal that was flawed, it was how it was done.