Porter has produced a book on U.S. policy in Vietnam from the mid-1950s to the mid-1960s that is full of interesting evidence and analysis in pursuit of a thesis that is wrong in key respects. It is a gallant effort, but, like many revisionist historians, Porter overreaches in attempting to prove that key policymakers understood the situation at the time just as he now understands it. He asserts that the period was characterized not by a delicate balance between superpowers but by U.S. predominance -- and that this helps explain risk taking in Vietnam. To be sure, policymakers' views on the shifting balance of power (especially when it came to Sino-Soviet relations) were certainly more nuanced than was let on in public, but none truly believed that the United States could act without constraint, as Porter suggests. Porter also argues that the United States' Vietnam policy was made more aggressive by a national security bureaucracy pushing its own preferences -- failing to recognize that their advice was always judged in terms of what the political marketplace would bear.