The book, "Axis of Aggressors: Countering the Cooperation of China, Russia, Iran and North Korea," examines how the four authoritarian governments support one another across military, economic, cyber and technology domains. During a potential confrontation between China and Taiwan, Montgomery said, North Korea could threaten South Korea or conduct limited attacks intended to pin down U.S. forces. "The longer they can entangle the United States, whether it was in Ukraine or in Iran, China and Russia are the primary beneficiaries," Montgomery said. Breedlove said China, Russia, Iran and North Korea "are not partners looking for cooperation with the U.S.," but governments seeking to "diminish and defeat" American power. Original article source: China, Russia, Iran and North Korea form 'axis of aggressors' that could overwhelm US, book warns