The standard CaD setup for battlefield play.
Squads 1 and 2 only on the wall. You attack with 1 and keep 2 on the wall.
Screenshot 1Tap your base. The ring of icons comes up. Tap the shield.
Screenshot 2Troop Reinforcement opens. Tap the green Wall Settings button at the bottom.
Screenshot 3Garrison. Four squads, each with a Join Defense tick. Tick 1 and 2 only โ untick 3 and 4. Defenders fight in order 1 โ 4, so put your strongest at 1 using the up/down arrows.