The two weaknesses principle is one of the most important techniques for exploiting an advantage. When you are facing your opponent in a tough game of chess and your opponent has developed a weakness it is your job to exploit the weakness in position that has been created. No matter how good your opponent is at chess, he or she will create weaknesses in his or her defensive structure as the game progresses. This is simply the normal flow of the game. You too will create weaknesses in your defensive structure as you become more aggressive on defense.
Your opponent will likely notice his or her weakness and attempt to securely defend this weakness. The weakness may not just be a vulnerable pawn, but may also be an invasion square that needs to be defended or a passed pawn that needs to be blocked. An experienced chess player will be able to defend one weakness without much difficulty. Try not to focus on this one weakness that your opponent is defending. Instead focus on finding or creating a second weakness for your opponent. By attacking this second weakness, and if necessary switching back to the first weakness, you are able to break down and eventually defeat your opponent's defense.
Experienced chess players will use this dual attack in the end game to win games. This can be an effective tactic in the middle game, but is probably used the most in the end game since there are so many weaknesses for your opponent to try to defend against. Conversely, try to make sure that you do not find yourself in this trap of defending two weaknesses at the same time. The player who finds themselves doing this will usually end up losing the game.