The constructivist turn in the study of world politics provides new impetus to studies of the political deliberations of human agents. The co-constitution of agents and structures implies the non-acceptability of accounts that fail to consider the interpretations human agents provide to structural conditions. But neither can we accept the reverse. Studies of the interpretations of political agents should adequately account for the structural constraints on those interpretations. This paper illustrates how easily agency studies can underestimate structural constraints by reference to a most serious and scholarly account of agency in the Vietnam War commitment decisions, Yuen Foong Khong's Analogies at War: Korea, Munich Dien Bien Phu and the Vietnam Decisions of 1965. The argumentative burden resides with those who offer accounts that hold or imply that agents acted from non-structural motives.