Harris was born in England, but his parents moved to Rhodesia (now Zimbabwe) when he was still a child. He was raised and educated there. At the outbreak of World War I, Harris joined the 1st Rhodesian Regiment, and served with then in South Africa and South West Africa (Namibia). In 1915 he returned to England and joined the Royal Flying Corps, and after the war transferred to the newly founded Royal Air Force in 1919. In the RAF he served in different functions in India, Iraq, and Iran. Since 1930 he was member of the air staff in the Middle East (1930-1932).
Harris contributed at this time to the development of terror bombing using delay-action bombs, which were then applied to keep down uprisings of the Iraqi tribes fighting against British occupation. In spite of the many civilian victims of these air raids, Harris is recorded as having remarked that "the only thing the Arab understands is the heavy hand."
Harris quickly rose through the RAF hierarchy, and was promoted to Air Commodore in 1937, Air Vice-Marshal in 1939, Air Marshal in 1941, and Commander in Chief of the Bomber Command in February 1942. At the time the RAF's night bombing role had had little effect on the German economy. By 1942 however, larger numbers of four-engined heavy bombers were becoming available, allowing for a change in tactics.
Harris developed the theory of attacking major industrial centers in order to deliberately destroy as many homes and houses as possible. This would displace the German workforce and reduce their ability to work. His calculations showed that his force would be able to destroy the majority of German houses located in cities quite quickly.
The plan was highly controversial even before it started. Others in the war effort did similar calculations and showed that he was inflating his numbers by several times, yet the plan was started in 1942. At first the effects were limited due to small numbers of planes on the raids, but aircraft production continued to increase while Harris pushed for huge raids with 1000 planes each. Harris launched the first of his "thousand bomber raids" against Cologne on May 30th, 1942.
Harris continued to believe that the bombing alone would force Germany to surrender. On a number of occasions he wrote to his superiors claiming the war would be over in a matter of months, first in August 1943, and then again in January 1944. However by this time Bomber Command had been involved in what became known as the Battle of Berlin, a series of massive raids on Berlin that started in November 1943, and lasted until March 1944. During this time the British lost 1,047 bombers, with a further 1,682 damaged, culminating in the disastrous raid on Nuremberg on March 30, 1944, when 94 bombers were shot down and 71 damaged, out of 795 aircraft.
With the leadup to the D-Day invasions in 1944, Harris was ordered to switch targets for the French rail network, a switch he protested because he felt the war was nearly won (again). By the end of the year the Allied forces were well inland, and in January 1945 he was allowed to resume his earlier policy. The several months of rest and refit had been useful to Bomber Command, and they were now able to put up well over 1,000 planes per raid. This culminated in the fire-bombing of the city of Dresden. Dresden, full of refugees from the former German east, was bombed over three days (February 13-15, 1945) resulting in a lethal firestorm which killed a large but widely disputed number of people. (See Bombing of Dresden in World War II.)
Critics of Harris, mostly in Germany, believe that the bombing was a war crime, and that Harris was a war criminal who, due to his luck in belonging to the winning party, in an act of Siegerjustiz was not held accountable at the Nuremberg Trials (Predecessor of the International Criminal Court for his deeds. Even within the British government, there was disquiet about the level of destruction created by the carpet-bombing of German cities.
Harris was made Marshal of the RAF in 1945 and retired soon after to write his story of Bomber Command's achievements in Bomber Offensive. Disappointed by the criticisms of his methods, Harris moved to South Africa, and was the manager of the South African Marine Corporation from 1946 to 1953. At that point the British appear to have changed their mind about his tactics, and Harris received an honour despite strong protests by the German government.
By modern standards of international law, the bombings ordered by Harris would be regarded as war crimes. However, defenders of Harris claim that he was responding to the German policy of total war, declared 1943 in the Berlin speech of Joseph Goebbels (being a response to British mass bombardment of German cities started in 1942) and the German use of strategic bombing against Guernica in 1937 (being a response of british bombing of iraqi tribes in 1932), and later in the Blitz pre-dated the Allied use. They also point out that his policy must have been at least implicitly endorsed by his political and military superiors, who could have replaced him with another officer if they had disapproved strongly.