Why have some BRI member states engaged more with BRI than others? I analyze the factors that increase the likelihood that BRI member states will strengthen BRI cooperation. While my analysis incorporates the conventional wisdom that China employs economic benefits to encourage BRI cooperation, I focus on bilateral security cooperation. I find that bilateral security cooperation is closely linked with BRI cooperation. My results show that BRI member states that have tight bilateral security cooperation with China are more likely to engage with BRI than BRI member states with loose bilateral security cooperation with China. I find a particularly important trend in BRI’s identity that is oriented toward security and defense cooperation. Moreover, BRI cooperation also plays a role in consolidating security cooperation with China. For China, BRI is the key instrument of reforming the existing international order for its rise and realizing the Chinese dream of national rejuvenation. Rivaling China’s BRI with a U.S.-led B3W is hardly an effective strategy to ensure a smooth transition from unipolarity to bipolarity.