The best defense is a good offense

"The best defense is a good offense" is an adage that has been applied to many fields of endeavor, including games and military combat. It is also known as the Strategic Offensive principle of war. Generally, the idea is that proactivity (a strong offensive action) instead of a passive attitude will preoccupy the opposition and ultimately hinder its ability to mount an opposing counterattack, leading to a strategic advantage.

George Washington wrote in 1799: "…make them believe, that offensive operations, often times, is the surest, if not the only (in some cases) means of defence".

Mao Zedong opined that "the only real defense is active defense", meaning defense for the purpose of counter-attacking and taking the offensive. Often success rests on destroying the enemy's ability to attack. This principle is paralleled in the writings of Machiavelli and Sun Tzu.

Some martial arts emphasise attack over defense. Wing Chun, for example, is a style of Kung Fu which uses the maxim: "The hand which strikes also blocks."

During World War I, Germany planned to attack France so as to quickly knock it out of the war, thereby reducing the Entente's numerical superiority and to free up German troops to head east and defeat Russia.

In some board games, such as Risk, one's ability to build up armies depends on aggressively attacking so as to acquire territory; however, in Risk, luck in rolling the dice is the ultimate determining factor. Players who fail to do so, and concentrate instead on holding the line against enemy attack, will likely end up in a weak position. In-depth info argues that this adage does not always apply: "When the battle rages between two players one should put every ounce of power in the offense, but when several players are involved, the political element changes this dynamic." In chess, one's ability to prevent enemy attacks often depends on maintaining the initiative – i.e., making a series of threats that the opponent must use his turns to parry, rather than launching his own attacks; thus, common tips used in conjunction with this adage are that the best way to upset your opponent’s plans is to become menacing and that the best way to stop an enemy threat to your own king is to attack his.

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Wikipedia