Answer: The answer is:
General Marshall was too valuable to remove from his position as army chief of staff
Step-by-step explanation:
Franklin Roosevelt, although overruling the chief of staff on this crucial strategic issue, came to regard him as so indispensable in Washington that, when the cross-Channel assault was finally mounted in 1944, he could not let Marshall assume command of the invasion force.
There for after proving himself on the battlefields of North Africa and Italy in 1942 and 1943, Eisenhower was appointed supreme commander of Operation Overlord–the Allied invasion of northwestern Europe.