Japan's invasion of China along with other "incidents" resulted in a shift toward an unfavorable view of Japan in the US and UK. In late 1937, Japanese navy aircraft dive-bombed and sank the USS "Panay", which Japan maintained was by mistake and for which she apologized and paid reparations. British gunboats were also fired upon, with one ship being damaged. Immediately afterward, the Japanese army conducted a massacre and rape in Nanking in which tens if not hundreds of thousands of civilians died. In mid-1938, Japanese warplanes shot down a civilian passenger aircraft, the first incident of its kind ever. Ultimately it was the United States demands that Japan leave China, and the associated sanctions imposed on Japan when she refused, that led to Japan's decision to expand her war to include the Western colonial powers. In anticipation of such a move in the Pacific, the IJN turned over responsibility for the air war in China to the IJA. By this time, the "China Incident" had become a quagmire for the IJA and tied down a substantial portion of its forces for the rest of World War II. Nonetheless, both the IJA and IJN had gained considerable experience in China, explaining in part their stunning successes during the months immediately following the attack on Pearl Harbor.