A key tenet of Sun Tzu's strategic philosophy is to attack the opposing side's weaknesses. "Now an army may be likened to water, for just as flowing water avoid the heights and hastens to the lowlands, so an army avoids strength and strikes weakness."
However, sometimes competitors seem invincible and few weaknesses are discernible. So another approach is to find ways to turn their strengths into weaknesses. For example, Coca-Cola's strength in the soft drink market was that it was the classic cola. With its long history as the favorite American drink, supported by decades of advertising, its position seemed unassailable. So Pepsi needed to find an approach that would work. It did so by turning Coke's strength into a weakness by coming out with the "Pepsi Generation" theme. This approach positioned Pepsi as the drink for the next generation of cola-drinkers, the youth market. It also positioned Coke as the drink for the older (and by implication, the old-fashioned) generation. With America's love affair with everything young Pepsi turned Coke's reputation as America's traditional drink from a strength to a weakness.