I think a great deal of pre WW2 ideals and doctrine date bake to the trenches of WW1 and it took some time for these ideas to fade based on new wartime experience.
My understanding was that the Germans chose an accurate GPMG with a high rate of fire as they found in WW1 that enemy infantry would move form cover to cover when attacking (when without a creaping barrage) so the time available to shoot at them was limited. It therefore maked sense to get a GPMG that could put a lot of rounds in the air in a short space of time to make the most of the brief periods when the enemy was in the open. The rest of the squad would carry the ammunition for the GPMG. They would largely be armed with an accurate rifle capable of only firing a few rounds of aimed fire when the enemy showed himself. Again this was deemed satisfactory as the Germans felt this would be all the fire the rifleman would be able to get off in the time allowed.
The British experience in WW1 was largely attacking. They found they needed a relatively light weight LMG with a lower rate of fire to put down suppressive fire on enemy position as the infantry advanced before finishing off the enemy with genades and the bayonet. This led to the a Bren gun.
It was only when the Germans experienced fighting both offensive and defensively that they required a weapon that could do both so the assault rifle was born out of this experience. Certainly there where prototypes of these weapons available pre WW2 but would any military invest serious funds into an proved and possibly unneeded weaopon when all experience points to weaopons available and in production being the best solution to potential battlefield problems.
However getting assult rifles earlier is possible. Simply sell it as a heavy SMG which is alegidly how the German Generals sold it to Hitler. So the Germans invest in this instead of the MP40 and as the war goes on they simply increase production.
My understanding was that the Germans chose an accurate GPMG with a high rate of fire as they found in WW1 that enemy infantry would move form cover to cover when attacking (when without a creaping barrage) so the time available to shoot at them was limited. It therefore maked sense to get a GPMG that could put a lot of rounds in the air in a short space of time to make the most of the brief periods when the enemy was in the open. The rest of the squad would carry the ammunition for the GPMG. They would largely be armed with an accurate rifle capable of only firing a few rounds of aimed fire when the enemy showed himself. Again this was deemed satisfactory as the Germans felt this would be all the fire the rifleman would be able to get off in the time allowed.
The British experience in WW1 was largely attacking. They found they needed a relatively light weight LMG with a lower rate of fire to put down suppressive fire on enemy position as the infantry advanced before finishing off the enemy with genades and the bayonet. This led to the a Bren gun.
It was only when the Germans experienced fighting both offensive and defensively that they required a weapon that could do both so the assault rifle was born out of this experience. Certainly there where prototypes of these weapons available pre WW2 but would any military invest serious funds into an proved and possibly unneeded weaopon when all experience points to weaopons available and in production being the best solution to potential battlefield problems.
However getting assult rifles earlier is possible. Simply sell it as a heavy SMG which is alegidly how the German Generals sold it to Hitler. So the Germans invest in this instead of the MP40 and as the war goes on they simply increase production.