Throughout the war, sloped armor was used on an increasing number of tanks. However it seems overmatching was a phonemon not understood till after the war. I notice not a lot of people seem not to have heard of the effect. Basically overmatching was an event that occurred if a shell hit sloped armor that was thinner then the diameter of the tank shell. Basically overmatching neglected the effective slope of the armor, making the armor not as strong if hit by a drastically thicker shell. Overmatching can be determined by a simple formula T/D (Thickness of armor / diameter of shell). Overmatching will not occur if T/D = 1.00 or greater, but will occur if T/D is less then 1.00. This can be factored into the formula: effective armor thickness*(1+( (slope multiplier -1)*overmatch factor)) To take a completely hypothetical example, say a 75mm shell hits 45mm armor sloped at 60 degrees, or basically a 75mm hitting the T-34s hull. Ordinarily the slope multiplier would be about 2.5 for 60 degree slope, giving about 112mm effective resistance. This chart can be used to calculate the effective armor sloped armor. However, because you have a high degree of overmatch here (75mm v 45mm) your algorithm calculates that for a 45/75 overmatch ratio the overmatch factor is say 0.6 (ie an overmatch factor of 1.00 represents no overmatch, the lower the figure the higher the overmatch) Then the effective armor of the target would be: effective armor thickness*(1+( (slope multiplier -1)*overmatch factor)) so in the example above the calculation would be: 45mm * (1+((2.5-1)*0.6)) = 45mm * (1+(1.5*0.6)) = 45mm * (1+0.9) = 45mm * 1.9 = 85.5 mm effective So in effect, the armor loses 26.5 mm of effective strength by being hit by a thicker shell. Thats a massive difference when you think about it. Hell, the common German 75 would not be able to penetrate 112mm of armor at ranges of 800m, but with overmatching, they were easily able to pierce 85mm of armor at 2000m. Now many tanks in WWII had sloped armor, especially American and Russian tanks. However, this event called overmatching made it so many of the tanks with sloped armor. The US TDs, and the sherman versons before the M4A2 and M4A3W series were all extreamly prone to this event. Also the T-34 always had this issue with its hull armor. Now there was an EXTREAM effect of overmatching literally causes an entire section of armor to catastrophically fail. The effect looks like someone took a massive sledgehammer to that section of armor. Literally, a 88mm shell will create a hole 3 feet in diameter to appear, and an massive amount of armor to shatter and fly into the tank. Needless to say the crew is slaughtered and ripped appart. This is all extreamly important to consider when talking about many tanks in WWII. For example the early shermans, as a result of poor armor quality (later fixed by 1943), and thin hull armor, was never as strong as it looked on paper with its effective armor. The shermans hull was suppost to be about 110mm of effective armor, but being 51mm, it suffered from overmatching. Its effective armor would likely be in the same range as the T-34 hulls armor, about 80-90mm, but adding in faulty armor quailty (85-90% according to some sources including Combat Mission), it could be as low as 70-80mm. This problem was not fixed until the Sherman (75)W and (76)W series rolled off, and also the British Sherman III (M4A2?) series. To eliminate 2 weak spots on the hull, the frontal armor was increased to 64mm, with a lesser slope, in effect, the armor because much more stronger, and much more effective vs 75mm shells. Tests from Combat mission shows the common 75 is unable to pierce the hull armor of these shermans at ranges of 800-1000m, though while its a simulator, its also a game.