Question

How did the volcanic ash at Iwo Jima affect the performance of artillery and naval bombardments by both the IJA and the US Navy

Answer 1

Once the Marines landed, they quickly found that the volcanic ash on the island was difficult to move in, got vehicles stuck, and slowed them down considerably. Marine Corps amtracs and medium tanks seen blasted by Japanese artillery after being bogged down in the soft black volcanic ash of Iwo Jima.

Source: Businessinsider.com