tactics. Provided that it is rational for them to act aggressively, great powers will likely pursue expansionist policies, which will bring them closer to hegemony. Since global hegemony is nearly impossible to attain due to the constraints of power projection across oceans and retaliation forces, the best end game status states can hope to reach is that of a regional hegemon dominating its own geographical area. This relentless quest for power inherently generates a state of "constant security competition, with the possibility of war always in the background". Only once regional hegemony is attained do great powers become status quo states. Balancing v. buck-passing The emphasis offensive neorealism puts on hegemony as states' end aim stands in sharp contrast to defensive neorealism's belief that state survival can be guaranteed at some point well short of hegemony. In a defensive neorealist mindset, security increments by power accumulation end up experiencing diminishing marginal returns where costs eventually outweigh benefits. Defensive neorealism posits that under anarchy there is a strong propensity for states to engage in balancing—states shouldering direct responsibility to maintain the existing balance of power—against threatening power-seeking states, which may in turn succeed in "jeopardiz[ing] the very survival of the maximizing state". This argument also applies to state behavior towards the most powerful state in the international system, as defensive neorealists note that an excessive concentration of power is self-defeating, triggering balancing countermoves. Mearsheimer challenges these claims by making the argument that it is rather difficult to estimate when states have reached a satisfactory amount of power short of hegemony and costly to rely extensively on balancing as an efficient power-checking method due to collective action issues. According to him, when a great power finds itself in a defensive posture trying to prevent rivals from gaining power at its expense, it can choose to engage in balancing or intervene by favoring buck-passing—transferring the responsibility to act onto other states while remaining on the sidelines. In order to determine the circumstances in which great powers behave according to one or the other, Mearsheimer builds on Waltz's defensive neorealism by including a second variable—geography—alongside the distribution of power. On one hand, the choice between balancing and buck-passing depends on whether the anarchic international system is of a bipolar, balanced, or unbalanced multipolar architecture. On another hand, state geographic location in terms of border sharing and stopping power of water also influences great powers'