Nixon pursued what he called "peace with honor", or perhaps an elusive victory by another name; yet critics called its aim a "decent interval". The policy was called Vietnamization. To end the war favorably he focused on the peace negotiations in Paris. There Henry Kissinger played the major role in bargaining with the North Vietnamese. Achieving peace proved difficult; in the meantime, casualties mounted. Although withdrawing great numbers of American troops, Nixon simultaneously escalated the air war. He increased the heavy bombing of Vietnam, also of Laos and Cambodia, and widened the scope of the conflict by invading Cambodia. While these actions sought to gain bargaining power at the Paris conference table, they also drew a "firestorm" of college protests in America. Kissinger describes a debate over the mining of Haiphong harbor, in which he criticizes Helms at CIA for his disapproval of the plan. In Kissinger's telling, here Helms' opposition reflected the bias of CIA analysts, "the most liberal school of thought in the government."