I played on Recruit difficulty and lost my first two castles as soon as I sailed away on a ship. Oh well, I moved on and sailed towards the green castle. I had enough troops to defeat the main Dark Elf on the shore. I'm now in the only green castle, slowly building up my army. Meanwhile, Blue has completely taken over my former territories, and Purple has sailed in to join him. And then the battle for power began! They took castles from each other, fought, and in the end, Blue won. With the army I had gathered in my last castle, I completed the mission. Of course, I could have acted more cautiously, but the war between Blue and Purple was amusing :D :D :D
Here's another alternative :D:smile54: