Mo. Rev. Stat. § 41.550: Credit for time in federal service.

For all purposes under this code, officers, warrant officers, flight officers and enlisted personnel of the organized militia who entered the active service of the United States in time of war or under an order or a call or draft by the President, or who hereafter enter such service under like conditions, shall be entitled to credit for time so served as if such service had been rendered in the state forces.