A decent strategy game, but nothing special when compared to the competition.
The game takes place during the warring states period in Japan. Now, KOEI's warring states game series is called "Nobunaga's Ambition" it didn't focus solely on Nobunaga Oda, it allowed you to play as any of the other rulers. In Shingen the Ruler, you're only able to play as Shingen Takeda, the Tiger of Kai. One thing I noticed, is that the Japanese version of the game, Takeda Shingen 2, was a bit more colorful and had a back-story after the title sequence, in the American version, the colors are a bit screwy and the title screen no longer has the back-story sequence.
Anyways, when you start the game you'll notice that you posses two territories out of about 22. You can check the status of any of the other rulers by selecting your ninja (it's pretty cool, when you select him in the menu there's a smoke bomb effect and he appears). One thing you'll notice is that your army is rank 0, while the lowest rank of your neighbors is 4, I find this whole thing a bit annoying. Rank is a sort of level, higher ranked armies will demolish low ranked armies with ease. In order to have an army that can actually kill things you must: attack an enemy and beat them on the field in order to make them retreat to their castle, gain your experience to increase your rank, then return home instead of taking their castle, or, spend countless turns trying to build a large army so that you'll stand a change against an army with a superior rank, or do both which is probably more logical. Now, combat is where I think this game shines the most, it doesn't have any fancy features like KOEI's Romance of the Three Kingdoms games do, it's pretty simple but with many possibilities. You can choose between manual and automatic combat. In manual, there are two long-ranged units, archers and riflemen, then you have calvary, infantry, lancers, and your headquarters unit (commander, it's called HQ in the game). The main objective is to kill the enemy HQ in twenty turns, or, in you're defending, just try to outlast the enemy for twenty turns. The ranged units can fire from inside castles and barricades to outside. Ranged units can't first past forest terrain, and are easily killed in melee combat. Calvary is the fastest and most powerful unit in the game, and the other two units, infantry and lancers, are pretty much cannon fodder/human shields for the ranged units. In automatic combat, the game just has each unit act is is they all attacked each other once per turn until the enemy HQ is dead, it's just about worthless since you'll lose expensive units like Riflemen and archers, which could easily be saved during manual combat.
All in all, the game play is decent. The city screen has too many options that are, quite frankly, totally useless. Such as the doctor, you can prevent a single city from getting a minor plague (that does almost no damage) for a few months for a few thousand gold. Or things like "Culture" and "disaster" which have no effect on the game at all.
The graphics are okay, some of the faces pictures for the rulers look a bit shoddy and the lancer unit looks like a fatty amoeba, but the terrain and map screen look fairly decent. Melee combat is shown by a pink swirly ball, and ranged units fire a volley of projectiles that look kind of like what they should be shooting.
The music is good, but it loops the same two or three songs during the majority of the game play. The sound effects are limited to: "beep", "blip", "squeak", "fa-shooon" and a muffled "Bam!"
Overall, this game is fairly decent, though, I feel like I'm a bit gentle on it for it being my first strategy game. A multiplayer feature would've made this game so much better, along with the ability to choose different rulers. This game could've rivaled KOEI's games, I'll admit that the game moves faster then they do, but it's not nearly as good.
If you want a good turn-based Strategy game for about the warring states, try playing Nobunaga's Ambition: Lord of Darkness for the SNES.