[Taqwus]

Among the more obvious differences are the heavy multiplayer and the pre-battle formations and scripting (think about it: tactical battles do not make sense in a 21-player game).

There are a *lot* of battlefield tactics which emerged for D2, many of which required significant preparation to be able to use in terms of mage selection, troop selection, magic items, and research, in addition to the obvious pre-battle assignment of orders and unit placement. Hell, there's everything from mass-exploding (Phoenix Pyre'd) reinvigorating Communicants to flying armies and storm/lightning-zapping the battlefield, to mass enslavement and super-combatants.

In terms of strategic depth, there's supply contraints (including a high-level abstraction of supply lines through the fortress contribution traced through friendly provinces), -substantial- research that offers lots of variety...