Strategic defense and attack of series systems when agents move sequentially

In the September 11, 2001, attack the defender moved first with a weak defense, and the attacker moved second with an overwhelming attack. One alternative is that the attacker moves first by announcing an attack, while the defender moves second to defend against that attack. Third, two ships in a simultaneous encounter cannot take the opponent's strategy as given. For a series system that the defender prefers should operate reliably, and the attacker prefers should operate unreliably, this article demonstrates that these three scenarios cause crucially different recommendations for defense and attack investments. For example, the defender prefers to move first rather than participate in a simultaneous game in a series system with two components. In contrast, an advantaged attacker in a series system prefers the simultaneous game since it does not want to expose which components are to be attacked. When the defender is advantaged in a series system, its first move deters the attacker. Deterrence is not possible in simultaneous games. When equally matched, both agents prefer to avoid the uncertain and costly simultaneous game that causes high investment costs. The results for the defender (attacker) in a parallel system are equivalent to the results for the attacker (defender) in a series system.