The Europa system from GDW/GRD was probably the most ambitious game system from a size perspective: If I recall rightly, 16 miles to the hex with division counters supplemented by regiments and battalions; aircraft at group level (or is it squadrons?)
This is a siege game which represents the defense of an airstrip by the equivalent of a French division against more than three Viet Minh infantry divisions supported by nine artillery battalions. The setting is a valley located in the highlands near the border between Vietnam and Laos in 1954. The game is divided into 21 turns, each of which represents three days. If the French have not surrendered at the end of the last turn, the French player wins. If they have surrendered, the Viet Minh player wins.