Cassini remained ambassador to China until 3 October 1896, and having gained the reputation of an astute, resourceful, and brilliant diplomat, he was appointed Ambassador to the United States in early 1898, shortly after the outbreak of the Spanish–American War. Cassini's tenure in Washington saw a great deal of activity on behalf of his Government as a result of the number of incidents which occurred during his posting—including the Kishinev incident, Russian occupation of Manchuria, and the Russo-Japanese War.