OK let’s get nerdy. In WWII, tank designers realised that sloped armour is more likely to deflect armour-piercing rounds than square armour. This reminds me of the aspect doctrine where square and opposition aspects are harder to handle than sextile or trine.

Here’s the Russian T-34. Note the sloped armour at the front of the tank. It had around 45mm (about 1.8 inches) of armour at the front of the tank.

Here’s the German Panzer IV. Note the front armour is much more square, in fact the upper part is almost a right angle. It had a lot more armour up front, about 80mm.

The interesting thing is, the T-34 with much less frontal armour was much harder to knock out with a frontal attack than the Panzer IV because the T-34 had sloped armour. Rounds were often deflected off the sloped armour, so the tank didn’t get the full impact.

Sloped armour also increases its thickness. But the deflection effect is also an important part of why sloped armour is effective.

This is reminiscent of the square and opposition aspects being hard or difficult aspects, while the sextile and trine are soft or easy aspects. The square and opposition hit with full force, while the sextile and trine deflect.

I learned a similar thing practising Karate in my teens. Our teacher taught us to turn our torso at an oblique angle when someone hits us in the stomach, to deflect the blow. Again, a full frontal attack hits very hard and hurts a lot, but by turning away you reduce the impact.