Complex sentence: It was argued that Dragoon diverted much-needed men and material away from the ongoing fighting at the Western front that could have been used, instead, to bolster the Italian front or to hasten the advance towards the Rhine by the Overlord forces.
Split into simpler sentences: It was argued that Dragoon diverted much needed men and material away from the ongoing fighting at the Western front. These should have been used instead to bolster the Italian front, or to hasten the advance towards the Rhine by the Overlord forces.