Through quantitative analysis of global data from 1980 to 2010 and brief consideration of the running case studies of late–Cold War Central America and Southern Africa, this chapter considers when states are likely to form relationships of security assistance (support ties). Although support ties carry costs, especially in the shadow of the potential interplay between the intergroup and intragroup security dilemmas, states still have incentives to offer and receive security assistance. Specifically, we observe that a support tie is more likely to form when the support recipient has stark security needs and is likely to be dependent on the supporter; when the supporter has high military capacity, has few existing outward support ties, and is a democracy; and when the recipient and supporter have congruent interests, are contiguous, are in a security assistance relationship with a common state, and have the same regime type.