George Mercer Brooke, United States Army officer, was born in Virginia and was commissioned first lieutenant in the Fifth United States Infantry on May 3, 1808. He was promoted to captain on May 1, 1810, and to major of the Twenty-third Infantry on May 1, 1814. On August 15, 1814, he was brevetted lieutenant colonel for his gallant defense of Fort Erie, Upper Canada; on September 17, 1814, he was brevetted colonel for "distinguished and meritorious service" in leading an attack on the British siege lines. On May 17, 1815, he was transferred to the Fourth Infantry and on January 27, 1819, to the Eighth. He was promoted to the substantive grade of lieutenant colonel on March 1, 1819, and transferred back to the Fourth on August 13 of the same year. He was brevetted brigadier general on September 17, 1824, for "ten years' faithful service in one grade," and was promoted to colonel commanding the Fifth Infantry on July 15, 1831. On August 1, 1844, he was appointed to the command of Military Department Number Four with responsibility for the states of Ohio, Indiana, Michigan, Wisconsin, Illinois, Iowa, and Missouri. And on June 10, 1846, he was appointed commander of the Western Division of the United States Army–the territory of the United States west of the Mississippi River–which he took over from Gen. Edmund P. Gaines, who had overstepped his authority by calling up thousands of militiamen for the Mexican War that the government could not use. Brooke, from his headquarters in New Orleans, was responsible for forwarding reinforcements and supplies to the field armies of generals Zachary Taylor and Winfield Scott in Mexico. Except for a time in November 1847 when he presided at the court-martial of Lt. Col. John Charles Frémont, Brooke continued in this capacity until July 1, 1848, when he was superseded by General Taylor. Thereafter Brooke briefly commanded Military Department Number One, which comprised Alabama, Mississippi, Louisiana, Tennessee, Kentucky, and Florida. On May 30, 1848, he was brevetted to major general for his service in the Mexican War, and on July 7, 1849, he was appointed to the command of Military Department Number Eight–roughly the eastern two-thirds of Texas–and served at that post until his death, on March 9, 1851.

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