D&D (Dungeons & Dragons) skirmish works at various sizes depending on whether you want to play with Dungeon grids/maps or without.
With grids 2'x2' is a big table (will use D&D Miniatures handbook rules).
Without grids tables are 2'x2', 2'x4' or 4'x4' depending on the actual rules you choose. You can use the skirmish rules from the Miniatures handbook, D&D Battlesystem skirmish or the Chainmail rules. Covers skirmish battles in dungeons, caverns, buildings or open ground.
Normandy Firefight is written for 1/35th (54mm) figures on a 4'x4' table, so playing with 1/72 (20mm) figures the designed table size becomes 2'x2', or smaller if you want to go 15mm or 10mm skirmish.