This trade off will come about whenever time is limited, there is competition between agents who are all potentially vulnerable to attack, the same resources each agent uses for offense could also be used for defense, and the primary goal of each is to win. There are many examples:
- In botany, plants grow their cells larger in number and size to maximize their exposure to the limited supply of sunlight. But plants also want their cells to be mature and specialized to protect against herbivores and pathogens. Growth (offense) and maturation (defense) rely on the same metabolism, so plants must choose between them. (see here)
- In soccer, Donovan's beautiful late goal against Algeria was not so so surprising, given that Algeria themselves had an incentive to score. This necessarily lowered their defenses, and allowed the US to capitalize with a glorious counter attack.
- In immunology, testosterone both develops sexual characteristics and hinders one's immune system. If you think of reproduction as offense and survival as defense, it is clear why you should be wary of macho guys come flu season. (see here)
- In national politics, war becomes more likely when conquest is easier. Nation states are well aware that by attacking weaker opponents they will still have enough resources available to defend themselves. (see here)
(Above photo credit goes to Lorianne DiSabato.)