Two Falchions (Divine Sword Contest in the Japanese version) is Chapter 4 of Fire Emblem: Awakening.
This battle consists of a fairly open arena with four staircases. The chapter is straightforward, and routing the enemy is a matter of moving all enemies into range of your units.
You start out in the bottom corner of the arena, with Marth on the other side. You may be tempted to simply move to the center of the arena, as there is a spot directly in the center where no enemy ranges cross. However, this can cause your units to become surrounded from the enemies on the left and right edges of the arena.
Instead, go ahead and put two strong units (probably Frederick and a Chrom paired up with someone with a higher movement like Sully) on each of the bottom two staircases. Let the knights kill themselves trying to beat on these characters. If you use Chrom for this, make sure to equip him with his rapier for this part of the chapter.
The two mages of the level aren't very dangerous, but can be troublesome if they are able to attack more than once on any given character. If you follow the strategy listed above, then the mages shouldn't be able to reach your characters on the first enemy phase. Use this time to kill them off.
The other enemies can be killed however you like. It doesn't really matter what you send after them, as long as you don't send in Lissa or an undertrained Donnel.
Marth is decently strong, and wields a Parallel Falchion. The easiest way to beat Marth is to simply send Frederick after him with either his silver lance or a javelin. If you haven't trained Frederick much, then you might want to pair him up with Sumia for a speed boost.