During World War II, Allied forces readily admitted that German tanks were superior to their own. The big question for Allied forces, then, was how many tanks Germany was producing. Here's how they reverse-engineered serial numbers to find out.

To solve the problem of determining production numbers, the Allied forces initially tried conventional intelligence gathering: spying, intercepting and decoding transmissions and interrogating captured enemies.

Via this method, the Allies deduced that from June 1940 to September 1942, the German military industrial complex churned out around 1,400 tanks each month. That number just didn't seem right. To put that number in context, Axis forces used "only" 1,200 tanks during the Battle of Stalingrad, an eight month battle with a total of almost two million casualties. So that number of 1,400 was likely way too high.

Obviously skeptical of the above result, the Allies looked for other methods of estimation. And then they found a critical clue: serial numbers.

Allied intelligence noticed each captured German tank contained a serial number unique to the tank. With careful observation, the Allies were able to determine that the serial numbers had a pattern denoting the order of tank production....