Many major crises are unexpected, unprecedented, and life-threatening on a large scale. The Dunkirk evacuation by the British in 1940 is a classic example, and the recent global COVID-19 pandemic is another one. Efficient public-private collaborations are critical in such "Dunkirk moments" for problem solving and crisis attenuation, with knowledge sharing and creation, in turn, forming the core of such collaborations. Based on a case of the COVID-19 pandemic, in which problems of facial mask manufacturing and distribution were solved through improvised public-private collaborations, this article systematically highlights the necessary conditions for successful public-private collaboration. Given the conditions thus identified, we further elaborate on the roles that knowledge plays as well as the nature of knowledge activation/creation in such a collaboration.