The "Bison", siG33 was indeed the first German self-propelled artillery. The problem with self-propelled artillery was when it was used as tanks. If tank-destroyers cannot be used as tanks because they do not have a turret, then self-propelled guns with no turret an no thick-armour are used to engage tanks is an insanity. This guns should be at the rear (third line) of the battle field, where they can provide supporting fire with big guns and move quickly. Being at the third line of the front, behind tanks and infantry (supossely) you would not have to worry about facing enemy tanks or infantry...

But when properly used they were lethal, because moving a conventional 150mm gun is horrendous! If the gun moves quickly, then it is going to smash ANYTHING. I like self-propelled guns a lot.

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"War is less costly than servitude, the choice is always between Verdun and Dachau." - Jean Dutourd, French veteran of both world wars

"A mon fils: depuis que tes yeux sont fermes les miens n’ont cessé de pleurir." - Mère française, Verdun