He made precision air attack, as both the most humane and effective means of achieving military success, a lifelong personal crusade that eventually became the key tenet of American airpower employment.

Unfortunately, his air bombardment campaign over Japan proved to be a failure due to various elements, such as the interference of a powerful and consistent jet stream in that nation's airspace.

He was replaced by General Curtis LeMay, who reoriented his air forces' tactics in reverse of Hansell's methods for an extremely destructive nighttime area fire bombing campaign over Japan.

[2] His grandfather, William Andrew Hansell, graduated from Georgia Military Institute and also served as an officer in the Confederate Army, first in the 35th Alabama, then as a topographical engineer.

[5][9] Partly as a result of this humiliation, Hansell declined an appointment to the United States Military Academy to attend the Georgia School of Technology, where he was a member of Sigma Nu.

Despite problems understanding differential equations,[10] and twice attempting to transfer to another school (which his father would not permit), he overcame his difficulties with complex mathematics and graduated in 1924 with a Bachelor of Science degree in mechanical engineering.

Advances in aviation in the 1920s led Hansell to undertake a career in aeronautical engineering, and to gain flying experience, he decided to join the United States Army Air Corps.

[2] General Ira C. Eaker described him as "nervous and high strung,"[14] and one biographer noted several incidents of imperious temper in social situations.

While frequent absences, long working hours, and Hansell's autocratic nature severely stressed their marriage during World War II,[18] they remained married for 56 years until his death in 1988.

While stationed at Langley, Hansell was involved in two minor accidents in aircraft he was piloting, and in early 1931 was forced to parachute to safety when his Boeing P-12 stalled during a test flight, going into an unrecoverable spin.

During that tour of duty he met Captain Claire L. Chennault, an instructor at the Tactical School, and joined "The Men on the Flying Trapeze",[22][nb 3] an Air Corps aerobatic and demonstration team.

[13] Hansell also worked with Captain Harold L. George, chief of the Tactical School's bombardment section, where his military interest shifted from pursuits to bombers.

[28] Hansell became a member of a group known as the "Bomber Mafia", ACTS instructors who were both outspoken proponents of the doctrine of daylight precision strategic bombardment and advocates for an independent Air Force.

[13] Among the students instructed by Hansell were Eaker, Twining, Elwood R. Quesada, Earle E. Partridge, Kenneth Wolfe, Orvil A. Anderson, John K. Cannon, and Newton Longfellow, all of whom became general officers and strategic airpower advocates during World War II.

[29] In September 1938, still a first lieutenant, Hansell entered the Command and General Staff School at Fort Leavenworth, Kansas, from which he was graduated in June 1939, shortly after promotion to captain.

"[35] Development of sources of information for such analyses also was primitive, and he used his assignment to OPB to recruit a number of civilian economic experts who had recently been commissioned in the military.

[36] On July 7, 1941, Hansell went to London, England, as a special observer attached to the military attaché, where he was privy to the inner workings of RAF intelligence and their target folders on the German industrial infrastructure.

The frantic efforts to meet deadlines, the disagreements, the uphill fight against entrenched and hostile opinion, the dedicated crusade for the new role of air power, the slumbering dread that we might be wrong—that we might persuade our leaders to take a path that would lead to disaster—put a heavy burden on all of us."

[53] He also flew combat in a B-17 to gain first-hand experience with daylight precision bombing, attacking the Longueau marshalling yard at Amiens, France, on August 20, 1942.

[55] Even though the Navy rejected the plan outright (because it did not participate in its writing)[56] and the Joint Chiefs of Staff did not accept it, presidential advisor Harry Hopkins recommended to Roosevelt that he follow the precepts unofficially, which was done.

Although Hansell did not personally participate in later strategic bombing operations against Germany, he had been instrumental in setting in motion the plans and policies that led to the near total destruction of German war industry.

[73] While in Washington on this task, he was "captured" by Arnold and accompanied him to the Quadrant Conference in August, where he personally briefed President Roosevelt on strategic bombing to that point.

[80] However Hansell's tenure was threatened from the start because his replacement on the Air Staff, Major General Lauris Norstad, did not support the concept of daylight precision bombing,[81] instead advocating massive destruction of Japanese cities by firebombing, a tactic that had been promoted in AAF planning circles as early as November 1943.

[84][nb 12] Furthermore, Hansell was soon prohibited from flying combat missions with his command, possibly because of limited knowledge of the atomic bomb or the perception that he knew the existence of Ultra.

Unknown at the time, his precision daylight attacks had succeeded, first in Japan's immediate and inefficient dispersion of its aircraft engine industry,[94] and later in terms of actual destruction caused by the final raid under his command.

[95][96] A more immediate legacy of his command was his creation, in conjunction with the U.S. Navy, of an effective air-sea rescue system that saved half of all B-29 crews downed at sea in 1945.

[100] Arnold by implication had erred in changing AAF strategy, especially taking into account the "deep and pervasive revulsion among the American people against strategic bombing of all sorts" that was a consequence.

[105] Conrad Crane took a somewhat different stance, arguing that despite the firebombing campaign in Japan, American air commanders throughout World War II and thereafter placed an emphasis on precision bombing and avoiding civilian casualties.

The use of precision guided weapons in the Gulf War and beyond, he wrote, demonstrated "continued adherence to precision-bombing doctrine and...significant progress toward the ideal...first envisioned" by Hansell and the other Air Corps Tactical School theorists.

In April 1953, Hansell was appointed the senior Air Force representative to the Weapons Systems Evaluation Group in the Research and Development Office of the Secretary of Defense, Washington, D.C.[110] He retired a second time from the USAF in 1955.