We wargamers have this genre called "Card Driven Games" (CDGs). Back in the early aughts, this was popularized by GMT to mean "games vaguely based on the ideas in Hannibal: Rome vs. Carthage, a game we know many of you like a lot". But things have sprawled now, and the CDG brand – to the extent it means anything at all anymore – has come to encompass a lot of games which have little or nothing in common. The Kaisar's Pirates, Empire of the Sun, and Combat Commander all show up on GMT's "CDG" page, for example.
What has diluted the idea for me is our propensity, as gamers, to focus on mechanism rather than something that actually matters. Cards, activation points, and events are mechanisms, but if that's all you know, you really know next to nothing about a game. Adding in the topic – say, the First World War – doesn't help much. We're now at the point where "a CDG on the First World War" would be an essentially vacuous description.
What made Hannibal great and distinct was not that it used cards, although clearly that was a powerful design choice. It was that it was a combination of a game that consistently managed tension well, keeping the players in constant, high-stakes conflict, combined with card design as an effective means of portraying the flavor of the period in several dimensions. In the 2nd Punic War, the loyalty of many Italian allies was fluid and having this cleanly abstracted in the card deck is great. The players know Syracuse sympathizes with the Carthaginian cause in a way that neither Roman nor Carthaginian leaders had much control over, and the cards provide an abstract way to play that out. The cards provide reasonable trade-offs between (say) using your limited political capital to get a reluctant general to seriously campaign, and reaching out to Macedon or raising auxiliaries. The system also portrays the Romans, with their rancorous and still-vaguely-Republican Senate, as having more inherent political friction than their less-representative Carthaginian foes, at least until Rome goes all-in as represented by the arrival of Scipio Africanus. All this is easy for me to say, but it requires a lot of attention to detail to get right, especially in a game of the size and scope of Hannibal.
Sekigahara is the first game to come along in a long time that manages, like Hannibal, to deliver the whole package: an elegant, playable, high-stakes game combined with highly evocative player decision-making. It's a game where risky, high-stakes battles produce great tension, and where hidden blocks give a lot of opportunity for bluffing and hoping. It plays in 90-120 minutes of high-speed action with a ruleset that can be easily taught at the game table. But what makes it a great game for me is that at the core of the design, the cards that drive the action, is an abstraction that makes sense and is historically flavorful.
In Sekigahara, you command an uneasy alliance of factions in the quest for control of Japan. Each player controls blocks of various strengths and types from four different factions. The shifting loyalties are controlled by a deck of cards (one for each player), with each card having a symbol for one of the factions. Once battle is joined, to get a block from a given clan to actually fight you need to play a matching card. Card-play alternates back and forth, with whoever is weaker needing to commit enough strength to close the gap. Large armies can be paper tigers due to the lack of sufficient political leverage to control them, while small armies that consist of dependable troops can be potent.
Of course, this being the period that it is, we have to have treachery. Each player has Loyalty Challenge cards which can cause blocks to switch sides if a clan's loyalty is borderline (i.e., if after committing it to battle you can't play an additional matching card to resist the challenge). While these challenges seem to be hard to time and rarely successful, they do make you nervous every time you commit a block with your last card for that clan and are dramatic when blocks actually defect.
Another interesting dynamic is the way cards are cycled. After battle, you replace all the cards you spent. So there isn't a net cost in cards to fight a battle, but the overall loyalty picture of the various clans tends to significantly change. Who knows what happened during the battle to cause the shift – it's below the level of the game – but nonetheless a battle where reach deep into your hand to call on the loyalty of your Samurai is a significant event with hard-to-predict consequences for loyalty amongst your factions. You may lose influence with some of your allies while another becomes more committed.
The thing about Sekigahara is that this relatively simple system creates a lot of the subtle nuance that is the hallmark of a great game. The strongest army is usually a hard core of good blocks from a single one of your factions which you can back up with matching loyalty cards, but this can be risky as a battle that uses up your cards and doesn't bring good replacements can leave that army completely ineffective. Armies of diverse clans don't pack as much punch but there is usually someone in there you can rely on if your opponent seizes the initiative. Battles can be fought for the secondary purposes of determining clan loyalty. You need to know when to press your luck because in the last battle your opponent cycled a bunch of cards and may be looking at a weak hand. And you have to know when to take a deep breath, give up significant tempo, and repair alliances by using the discard and draw action.
The last important thing that makes Sekigahara tick is the geographical layout. The game revolves around 9 castles on the board; Tokugawa starts with 5, Ishida with 4. Both players start with strong bases on opposite sides of the board, and isolated castles strung out in enemy territory. Both sides need to be super-aggressive about taking out the opponent's armies that start in their territory and consolidating control over castles. Both sides face tough choices about how to balance aggression between marching on their opponent's core areas (and relieving pressure on their far-flung outposts) against leaving enough troops behind to clean up their own backfield. Both sides face a huge amount of pressure to take the battle to the enemy, which is great and keeps the game dynamic and moving.
The designer's notes to the game – which are recommended reading if you want to understand what Matthew Calkins has done here – talks about how important personal loyalty was to this conflict, and how the game was designed with that idea at the core. I think Sekigahara does a great job of both capturing something important and interesting about the period and conflict, and bringing it to the tabletop in an elegant, highly-playable, compelling package.