In 1901, American-flagged merchant vessels returned to the Yangtze when Standard Oil Company placed a steam-powered tanker in service on the lower river. Within the decade, several small motorships began hauling kerosene, the principal petroleum product used in China for that company. At the same time, the United States Navy acquired four Spanish vessels (the gunboats , , , and ), which it had seized in the Philippines during the Spanish–American War. These vessels became the core of the Yangtze River patrol for the first dozen years of the 20th century, but they lacked the power to go beyond Ichang onto the more difficult stretches of the river.