During August 1945, Brown was appointed deputy chief of staff of Sixth Army under General Walter Krueger. As an experienced staff officer, he participated in the planning of Operation Downfall, planned invasion to Japan. However, the Empire of Japan surrendered on September 2, 1945, and the operation was cancelled. Brown was decorated with the Bronze Star Medal for his participation in the planning. While he served in this capacity, he also participated in the Occupation of Japan.