Have Krom talk to Callum and Double with him after talking. Move Callum next to Frederick and pass him a Javelin and Krom. Attack either the archer/soldier in the left group using the Javelin. Keep everyone else out of range but as close as possible so they can mop up the remaining enemies on the second turn. The casualties you suffered in the last chapter are probably going to bite you in the arse hard, here. With no casualties you have just enough firepower to clean up all the enemies on the left side.
Next you need to intercept the enemies on the right, position Frederick so he's just in range (he should be able to take on an archer + another unit), and repeat, pulling back each turn. You should be able to weaken the enemies enough to finish them off with a concerted attack by the time they chase you to the left side.
If you're having trouble with insufficient firepower because of the casualties, it might be helpful to get creative with partner swaps. For example, Liz can't attack, but if you move her next to Frederick and pull Krom off him, switch and attack, it's as if she got a turn to attack.
Also worth a mention - an amusing alternative strategy is to not
talk to Callum and instead use him as an invisible shield that you can pass through but the enemies can't. Though you'll probably get sandwiched anyway, and getting the Javelin on the first turn is much more important.
Edited by No. 3, 21 June 2012 - 06:48 AM.