With the fall of France, the need for infantry tanks to advance with troops started to be replaced with a need for Assault tanks, a new class with heavier frontal armour to take on battlefield defences. Infantry tanks proved capable in this new role however, and the designation was rarely applied outside of experimental production. The term saw limited use with both British and US forces in joint development. Hobart would later return to Martel's idea of Engineer tanks in the 1944 run-up to D-Day with Hobarts Funnies, and specialised tanks became a core component of the modern battlefield.