The Mass Battle rules in Savage Worlds are a great way of abstracting large-scale battles, allowing the player characters to influence the outcome (albeit at great risk) but also simulating the clash of armies. Unfortunately, they can look a little strange when applied to some of the situations that come up in RPGs, because the strength of the two contesting armies comes only from their size. For roughly equivalent forces, this makes sense, but I wouldn't want to bet on the 1000 man pike and shot regiment taking on 3 Abrams tanks. Crazy? Not in RIFTS, it isn't. So how do you manage a fight like that? Aaron Huss and the Ultimate Game Mechanics Guide: Ground Warfare have the answer.
The Ground Warfare guide introduces mechanics for assessing the composition of different forces, so that you can adjust for the armor and firepower benefits of that Abrams tank, or, for that matter, of mechs, dragons, or demigods. Adjusting the tokens provided to each side for the mass battle rules helps represent those different compositions. Other mechanics look at the difference between ranged and melee focused armies (I'm talking to you, Henry V), alternate options for player action during battle, and improved rules for sieges. If you'd like your campaign to include large-scale epic battles a la Lord of the Rings or Star Wars, consider picking up the Ultimate Game Mechanics Guide: Ground Warfare to add some extra meat to those encounters.