When David slew Goliath, David went for Goliath's weak point. It was also Goliath's strongest.
When you have a short battle, you go for the kill as quickly as possible, especially if you have a smaller force. Attacking an opponent's weak link only allows them to reinforce and to strike back. With a larger force on hand, they may likely overwhelm you.
Always go for the enemy's strongest point. Find a way to make their strength their weakness and you will have a better route towards winning the battle.
