This study focuses on Colonial-Korean horse administration during the period of aggressive war (1931-1945) and analyzes: ①The progress of the 'Second Phase Korean Horse Production Plan' which began after the Manchurian War(1931).②The twists and turns surrounding the establishment of the 'First Phase Korean Horse Administration Plan' led by the Governor-General of Chosen before and after the Sino-Japanese War.③ The failure of the privately-driven horse production policies during the Pacific War, including the emotional movement such as the “Healthy Horse National Service Movement” and the process of frugal mobilization. These analyses confirm the deceptive nature of the colonial horse administration. To summarize the findings: Following the Manchurian Incident, the demand for military horses increased, leading the Governor-General’s office to plan ‘the first phase of horse production’ starting in 1932. This plan aimed to increase the number of military-eligible horses to 30,000, focusing on the three northern provinces of Korea. However, from 1935, Japan urged the Governor-General to expand the number of horses to 40,000 over an 18-year period. This was known as Japan's 'Second Phase Horse Administration Plan (1932-1936)'. Japan dismissed the Governor-General’s request for financial support and demanded an increase of 50,000 horses over the 18 years. In response, the Governor- General claimed that the 'reality of Korea' justified a target of increasing 30,000 horses over 15 years. After about a year of negotiation, the Korean Horse Administration 15-Year Plan was settled, aiming to increase the number of horses by 40,000 over 15 years. However, due to financial issues, the plan did not fully begin implementation until 1939. In the case of Hamnam, the second horse administration area, the plan was to secure approximately 16,000 horses from 1939 to 1951, primarily through the importation of about 9,000 horses from Japan. The plan emphasized importation over domestic production. In reality, the increase in the number of horses did not proceed as planned. The number of horses showed a decreasing trend up until 1938, and the numbers of donkeys and mules sharply declined until 1943. After 1938, Japan reduced Korea's role in its horse administration plans and increased the focus on Manchuria, leading to a stagnation of the plan. The Governor-General attributed this failure not to policy issues but to a lack of knowledge or enthusiasm among private breeders. With the outbreak of the Pacific War, the Governor-General anticipated a surge in demand for military horses. Consequently, the responsibilities of the existing 'Korean Horse Administration 15-Year Plan' were transferred to the semi-official private organization, the Korean Horse Society, and the National Mobilization Association, in an attempt to increase the voluntary efforts of horse production. The Korean Horse Society was established on April 1, 1942. However, its establishment undermined the plan to increase military-eligible horses through breeding with high-quality horses from Japan. Instead, the focus shifted to a so-called 'Korean Horse Mobilization Policy', which aimed to convert existing Korean horses into military horses. Yet, by early 1944, the increase in military horses had not been achieved according to the plan. As noted in the Korean Horse Society Chairman’s address on March 1, 1944, during the Healthy Horse National Service Movement, many of the horses in the horse administration area were 'useless broken-down horses.' In summary, while the Governor-General boasted about increasing the number of military horses to 40,000, the priority from the beginning was mobilizing Korean horses and importing Japanese horses rather than actual production. Even the Korean military did not trust Korean horses and preferred mobilization and importation over production.