As we enter an era of hot wars in a warming world, cooling technologies and infrastructures are becoming ever more critical. These range from dissipating the heat generated by experimental weapons, such as high-energy laser systems, to managing the enormous thermal demands of data infrastructures that underpin the automation of killing. This talk explores military cooling through the biopolitical dimensions of military blood transfusion networks and the relationship between military cooling technologies of sustenance and death. Focusing on the US military during the Vietnam War, the talk explores the development, use and cultures of the US military “blood chain”, a blood transfusion network reliant on cryo-technology. The talk explores what the blood chain reveals about “cryo-warfare”, US imperial power in Asia and its conduct of battle during the Cold War.