A good tip for moving cruesade armies is to move them a little bit at a time and keep on moving them untill you can move them no more on each turn. The reason i say this is so you can pick the most direct route if you just click on the edge of the green they end up going all around the house. Also moving your army a bit at a time also stops you getting stopped dead in your tracks by another army. If you move a bit at a time you can see the other army then change direction so you dont lose movements per turn which is the biggest killer for me when it comes to desertions.