An Analysis of the U.S. Alliance System(Wang Wei) The United States has established a broad alliance system, under which each ally plays a role and enjoys alliance benefit in return. The United States is prone to obscure treaty obligation and avoid overcommitment, but it seeks to balance commitment among its allies. Such alliance behavior has a solid institutional basis. With a comparative analysis of the contents of various alliance agreements involving the United States, this article tries to define the limits of U.S. security commitment. It contends that alliances, built up in different strategic needs and with different levels of social identification, assume different responsibilities and, accordingly, carry out different U.S. security commitments. The U.S. alliances, forged with common interests, strong role identification and therefore powerful institutional linkage, can endure hard times and survive the changing circumstances. In contrast, alliances based on mere interest but without solid social identification cannot strengthen substantive institutional link that can stand against changes of political environment.