Lange made his name on the international stage with his steadfast leadership in the anti-nuclear weapons movement. His government refused to allow nuclear-capable ships into New Zealand's territorial waters, a policy the country continues to this day. In February 1985, Lange famously rejected the arrival of the USS "Buchanan", supported by a recommendation from the acting prime minister Geoffrey Palmer. The ship was not armed with nuclear weapons but was capable of carrying them. This displeased the United States; in response, all intelligence flow to New Zealand was stopped and joint military exercises were cancelled. In 1985, there were 22 programmed exercises canceled or restructured, resulting in approximately 6,000 man-days of training being taken away.