A study of the history of the US Navy's gunboats and their role in building a worldwide American naval presence abroad and in combat, from the Yangtze era through to World War II.

For more than half a century, American gunboats were the ships often responsible for policing small crises and provided deterrence and fast-response capabilities around the world – showing the flag, landing armed parties, patrolling river and littoral areas, and protecting ex-pats. Many US gunboats were built, purchased or reassembled overseas where they usually served out their entire careers. Many were also captured from the Spanish during the 1898 war, raised from shallow graves, refurbished, and commissioned into USN service.

The major operational theatres associated with the US gunboats were the pre-1898 cruises and patrols of the earliest steel gunboats, the Spanish-American War of 1898 (both the Philippines and the Caribbean), the guerrilla wars of the early 20th century Philippines and Latin America, the Asiatic Fleet and famous Yangtze Patrol of the 1890s–1930s, and finally World War II, which largely entailed operations in China, the Philippines, the Dutch East Indies, Alaska, and on convoy routes.

It was Japan’s sudden 1941–1942 'Centrifugal Offensive' that effectively spelled the beginning of the end not just of most American gunboats, but also the century-old world order in Asia that had provided US gunboats with their primary mission.