Now that Gatecrash is out, its guilds - Boros, Simic, Orzhov, Gruul, and Dimir - have enjoyed massive popularity. Not only are they being played in Limited and Standard Constructed, but their color combinations are getting used pretty heavily in other formats as well. Ravnica, of course, did not invent multicolor cards; there have been plenty of other bicolor cards printed throughout Magic's history that have nothing to do with the guilds. These six cards, though not Boros-affiliated, are in the Legion's red and white colors and will allow Boros decks to marshal their forces and dominate the ways of war. Take a look:
6. Bull Cerodon
Boros decks are a little bit one-track. They're good - probably the best - at one thing: weenie aggro. In other respects, they are found wanting, particularly with fatties and late-game defenses. If it comes down to turn 5 or 6 or 7 or later, the Legion is probably going to find itself rather outclassed when it comes to fat threats and finishers, and unable to deal with them in time. Fortunately, there is Bull Cerodon to sit comfortably in the six-mana slot in Boros's curve. The Shards of Alara groundpounder from the subplane of Naya hits the ground running with haste, and makes sure you're never unguarded with vigilance. For a guild that's about all-out attacks, this is comfortingly hard-to-kill in combat, and will happily eat up any small-to-midrange ground-based attackers your opponent throws at you if they somehow survive until their next turn.
The other aspect of combat that red and white have regrettable deficiencies in is evasion. But what if I told you there was a card in Boros colors that was effectively an unblockable 3/2 for four mana that can throw its combat damage around wherever you want it to in order to blow up potential blockers or threats? Yes, Soltari Guerrillas, the only multicolor (and also the only part-red) card with shadow, fits nicely with the Boros Legion for two reasons: It's a consistent attacker (for reliable battalion-triggering) that's basically impossible to deal with in combat, and it can make sure your other guys get through in subsequent turns. Oh, and it's utterly apocalyptic if you can manage to give it double strike. Players may be wary of a card with stats like that for four mana nowadays - hey, creatures weren't quite as efficient in Tempest - but it's a testament to how strong this is that it's still playable as a removal-blaster fifteen years later.
An aggro deck as fast as Boros, by definition, plays far, far more lands than it should ideally need. So how can it make sure its late-game land drops are actually relevant? One way is to play a lot of creatures with activated abilities, like Foundry Champion, which is at least a satisfactory solution, but perhaps not quite enough. Then there's Goblin Trenches, which turns lands into win. For what matters more to red-white aggro: lands, or Raise the Alarm/Dragon Fodder? Here's the upshot: As long as you're willing to make the greatest sacrifice of all - your very capacity to play the game of Magic - your army will multiply and be as numerous as the grains of sand in the desert. There's a pleasing asceticism to the notion of sacrificing lands in a Boros context, and this is more or less a guaranteed battalion-igniter. You'll thank me when you need to push through juuuust a few more unblocked hits for the win.
No deck type wants for anthem effects more than this one does. The simple math is: the more boots on the ground (or wings in the air) you have, the more value you're getting out of your mass pump. +1/+1 to both of two 4/4s is enough to shave off half a life total. +1/+1 to all of five 2/2s is nearly enough for a player kill. Let's do some more math - Glory of Warfare is a four-mana enchantment that grants mass +2/+0 to your creatures on your turn (aka when it counts). This means if you can attack unblocked seven times with 1/1s, five with 2/2s, or four with 3/3s, that is 20 life gone. Assuming you didn't goldfish on your first three turns, we can assume that your opponent's life total is probably somewhere in the 10-12 range, reasonably halving the number of attacks they can stand. The point is: +2 power en masse for four mana is an insane deal, and the blocker/mass burn (your own Volcanic Fallout and other instants included)-deterring +0/+2 on your opponents' turns is just icing on the cake. Heck, the mere fact that Fortress Cyclops exists proves that Glory of Warfare is meant for Boros decks.
Boros is no stranger to legendary Angels - its guildmasters have been Razia and Aurelia, after all. So what's the harm in calling on a third lady of war to lead the Legion? Gisela might be expensive - probably enough to turn off a lot of Boros players - but she's more of a guaranteed victory than either Razia or Aurelia. In fact, the great thing about Gisela is she doesn't even have to attack to ensure you win - the mere fact of her static abilities doubling your damage output will usually be good enough. Also unlike the Legion's guildmasters, Gisela has the good sense to guard you from the desperate final assaults of your opponents with that damage-halving ability. In other words, if you're going to splurge for an expensive legendary Angel, why not go for the most explosive one that exists?
This number 1 is so obvious that it speaks for itself. Additional combat phases are the greatest boon to Boros decks that a player could possibly ask for. Waves of Aggression is just as good at granting them over and over and over again as Aurelia is, and is also cheaper and harder to remove. I would like to say a handful of more words about it anyway: attack attack attack attack attack attack attack attack attack...