D-Day requires two units that hadn't previously been introduced to the Tank Battle series : paratroopers and landing craft. Both come with quirks that make them a bit gamey.
Many missions use landing craft that come in two varieties: regular and gigantic. In order to land heavy equipment, such as tanks, on the beach, the Allies used LCT (Landing Craft, Tank). In the game, these occupy 7(!?!) hexes and hold up to three units. Alternatively, LCVP (Landing Craft, Vehicle, Personnel AKA Higgins boats) occupy one hex and hold two units. The trick is maneuvering LCTs so that armor can provide cover for infantry. It can also be a struggle to unload engineers early so they can clear mines. Landing craft blocking the next wave of units seems like an authentic problem the Allies faced. Somewhat less authentic is mortars and artillery raining shells on the enemy while still on the landing craft. The main advantage is they aren't clogging the beaches.
Paratroopers work like off-map artillery except a new unit materializes in an empty hex. This can be very convenient to capture strategic and control points. The landing zone must be within the visible area of the map and not on a building or an enemy unit. Otherwise, you have complete freedom and the drop will go exactly as you order. While that's handy, it's hard to connect the mechanism with the historical reality. Real airborne drops were chaotic and disorganized. Paratroopers often found themselves in unknown territory far from their objectives. For the sake of the game, I suppose deterministic drops are best. But I wish there were some way to simulate the confusion of the actual invasion.
Speaking of historical simulation, the maps of the beaches were designed to reflect the actual battlefields including German pillboxes, obstructions and fortifications. Other missions are more thematic than modeled directly after Normandy events. Frankly, the historical missions tend to be tedious. It's just a lot of maneuvering and slow chipping away at German fortifications. I suppose that's what it was really like. One way the level designers enlivened these missions is by sub-goals. If the Allies capture certain points, they can stop German artillery.
Overall, this is a worthy addition to the Tank Battle series with novel features.