Tanks are designed to be resistant to most threats on the battlefield, like small arms fire, large calibre weapons, toxic battlefield conditions and not to mention other tanks. Without sufficient firepower, a tank is a terrifying force to be reckoned with.
However, while they may be able to survive a hail of machine gun fire, artillery barrages and high velocity anti tank guns, if they come up against a simple river, swamp or ditch, a tank isn’t so mighty.
Because of their heft, tanks usually have poor power to weight ratios, and lack traction on extreme terrain. Meaning they do not have the ability to tackle wide trenches, steep hills or swampy ground. This fact is well known by militaries, so they usually provide tanks with lots of support, like portable bridges and fascines. Unfortunately, in times of war, this level of preparation can become secondary to the objective.
The huge weight of a tank in a relatively small area means if they attempt to use a locally built bridge, especially ones built before WW2, which weren’t expected to support much more than a large truck, it can end in watery disaster. This scenario wasn’t an uncommon one during WW2, as the rapid and fluid pace of combat meant decisions had to made fast, even if they were a gamble.
Some of the heavier German tanks were able to be sealed up, and wade through a river with support. This process took time and many commanders simply went for the fastest option. When its between a Soviet 85 mm round or a creaky old bridge, you can see why!
This didn’t always go to plan – here are some examples of when those risks didn’t pay off.