Pokemon + Nobunaga's Ambition = Super addicting strategy game that can easily consume over 100 hours.
Pokemon Conquest mashes the collective and strategic nature of the Pokemon series with the gameplay element of Nobunaga's Ambition and leaves us with one of the longest and most addicting DS titles I've ever played.
The main storyline can take you anywhere from 10-50 hours depending on how much you take advantage of it. In the main story line, you get more access to the side characters than you do in any of the extra missions available to you after you beat the game so I would recommend using that opportunity to link as many of your warriors to their perfect Pokemon as possible.
In this game, Pokemon levels are done through percentages, the closer it is to 100%, the more powerful your warrior's Pokemon is. Every side warrior has one specific Pokemon that they can achieve 100% with while some of the warlords have two (in your Hero/Heroines's case, all the Eevee evolutions and one legendary).
The difficulty in the main story line is fairly easy but requires some grinding as your army can only get stronger while the opposing kingdoms remain the same. It is very important that you take the correct Pokemon into battle because even if the opponent has one Pokemon that is resistant to the rest of your Pokemon, it can mean defeat through running out of time. In the story based missions after, the opposing army now has a mind of its own and will strengthen itself while you strengthen your army so it ups the difficulty quite a bit, especially since each kingdom no longer has a specific element of Pokemon.
The battle system is quite fun but can be frustrating at times, especially with the accuracy percentage. Too many times have I seen 85% hit rate yet I would miss twice or three times in a row while my other Pokemon with 40% hit rate hits the first time. Also status effects can easily turn what was supposed to be an easy battle into a difficult one so if you're going against electric, fire, or poison Pokemon be prepared.
This game does require a lot of management in where to place each of your 100+ warriors, building up each of your kingdoms, earning gold, linking/leveling up Pokemon, battling opposing kingdoms and defending your own so there is a lot to think about.
Overall, this is easily one of the best values in the DS library and a game I will probably still be playing months from now. If you love strategy games and Pokemon, I highly recommend you get Pokemon Conquest.