Age of Empires: Castle Siege

to play multiplayer battles, you click on the swords in the bottom left, and click "find opponents". it costs 10 food (more in later ages) and uses up the troops that you send. you will do this once during the tutorial. after upgrading the keep and reaching the Second Age you are free to progress as you please. just win 19 more battles and you will earn this achievement. it's a good way to spend time while you are waiting for your buildings to progress and you will earn Food and Lumber as well. don't forget to train more troops each time.

To WIN Multiplayer battles you need to defeat the Keep or take 50% and above in resources - you can win the battle by simply nicking half what is on offer. The best fights for these latter ones are where they have resources outside the walls, or a large group within. Take out the outside resources tactically - ie do not commit everyone if a couple of units will do and keep and eye on the % counter. Too many times I have attacked a Uni for the flags when knocking a farm flat would have taken me over 50%.

To hit the Keeps you need Belisarius as a hero with the ability to undermine walls, and despite being the first Byzantine hero is worth having. Throw in Rurik of Russia with his Strike ability and you have a pretty good team - Oh! Of course that means you need to upgrade to TWO hero slots through research. Both will also upgrade to Two Undermines or Two Strikes respectively. Once Belisarius hots the walls, send Rurik in to hit the Keep then storm it with everything you have left. That should win by taking out the Keep.