“I don’t see a need for larger artillery than our standard 155 mm at this time.”
They have a devastating effect on massed things like artillery and vehicles. Also on Japs hiding in caves/bunkers.
Artillery is mandatory. Size was the point/debate.
Sizes have tradeoffs. Time to fire. Crew sizes to load/reload. Blast radius/depth. Quantity of munitions that can be transported.
Don’t fight the last war.