Historian Bret Devereaux has a long but well worth reading post on the longstanding debate over the role of airpower in war.
Before we dive in, we need to define what makes certain uses of airpower strategic
because strategic airpower isn’t the only kind. The reason for the
definition will emerge pretty quickly when we talk about origins, but
let’s get it out of the way here: strategic airpower is the use of attack by air (read: bombing) to achieve ‘strategic effects.’
Now that formal definition is a bit tautological, but it becomes
clarifying when we talk about what we mean by strategic effects; these
are effects that aim to alter enemy policy or win the war on their own.
Put another way, if you use aircraft to attack enemy units in support of a ground operation (like an invasion), that would be tactical airpower; the airpower is a tactic
that aims to win a battle which is still primarily a ground (or naval)
battle. We often call this kind of airpower ‘close air support’ but not
all tactical airpower is CAS. If you instead use airpower to shape
ground operations – for instance by attacking infrastructure (like
bridges or railroads) or by bombing enemy units to force them to stay
put (often by forcing them to move only at night) – that’s operational
airpower. The most common form of this kind of airpower is
‘interdiction’ bombing, which aims to slow down enemy ground movements
so that friendly units can out-maneuver them in larger-scale sweeping
movements.
By contrast strategic airpower aims to produce effects at
the strategic (that is, top-most) level on its own. Sometimes that is
quite blunt: strategic airpower aims to win the war on its own without
reference to ground forces, or at least advance the ball on winning a
conflict or achieving a desired end-state (that is, the airpower may not
be the only think producing strategic effects). Of course
strategic effects can go beyond ‘winning the war’ – coercing or
deterring another power are both strategic effects as well, forcing the
enemy to redefine their strategy. That said, as we’ll see, this
initially very expansive definition of strategic airpower really narrows
quite quickly. Aircraft cannot generally hold ground,
administer territory, build trust, establish institutions, or
consolidate gains, so using airpower rapidly becomes a question of ‘what
to bomb’ because delivering firepower is what those aircraft can do.
As an aside, this sort of cabined definition of airpower and thus strategic airpower has always been frustrating to me. It is
how airpower is often discussed, so it’s how I am going to discuss it,
but of course aircraft can move more than bombs. Aircraft might move
troops – that’s an operational use of airpower – but they can also move
goods and supplies. Arguably the most successful example of strategic
airpower use anywhere, ever is the Berlin Airlift, which was a
pure airpower operation that comprehensively defeated a major Soviet
strategic aim, and yet the U.S. Air Force is far more built around
strategic bombing than it is around strategic humanitarian airlift (it does the
latter, but the Army and the Navy, rather than the Air Force, tend to
take the lead in long-distance humanitarian operations). Nevertheless
that definition – excessively narrow, I would argue – is a clear
product of the history of strategic airpower, so let’s start there.
...
One of those interwar theorists was Giulio Douhet (1869-1930), an Italian who had served during the First World War. Douhet wasn’t the only bomber advocate or even the most influential at the time – in part because Italy was singularly unprepared to actually capitalize on the bomber as a machine, given that it was woefully under-industrialized and bomber-warfare was perhaps the most industrial sort of warfare on offer at the time (short of naval warfare) – but his writings exemplify a lot of the thinking at the time, particularly his The Command of the Air (1921).2 But figures like Hugh Trenchard in Britain or Billy Mitchell in the United States were driving similar arguments, with similar technological and institutional implications. But first, we need to get the ideas.
...
Now before we move forward, I think we want to unpack that vision just a
bit, because there are actually quite a few assumptions there. First,
Douhet is assuming that there will be no way to locate or intercept the
bombers in the vastness of the sky, that they will be able to accurately
navigate to and strike their targets (which are, in the event, major
cities) and be able to carry sufficient explosive payloads to destroy
those targets. But the largest assumption of all is that the
application of explosives to cities would lead to collapsing civilian
morale and peace; it was a wholly untested assumption, which was about
to become an extremely well-tested assumption. But for
Douhet’s theory to work, all of those assumptions in the chain – lack of
interception, effective delivery of munitions, sufficient munitions to
deliver and bombing triggering morale collapse – needed to be true. In the event, none of them were.
This is not at all how the standard narrative is supposed to go. Advocates for new technology are inevitably visionaries unappreciated in their own time but vindicated by history while those who disagreed with them are revealed to be fools and luddites. Hell, Gary Cooper played Billy Mitchell in the movie.
And before anyone complains that it's unfair to lump Mitchell in with Douhet, let's check in with Wikipedia. [emphasis added.]
In 1922, while in Europe for General Patrick, Mitchell met the Italian air power theorist Giulio Douhet and soon afterwards an excerpted translation of Douhet's The Command of the Air began to circulate in the Air Service. In 1924, Gen. Patrick again dispatched him on an inspection tour, this time to Hawaii and Asia, to get him off the front pages. Mitchell came back with a 324-page report that predicted future war with Japan, including the attack on Pearl Harbor. Of note, Mitchell discounted the value of aircraft carriers in an attack on the Hawaiian Islands, believing they were of little practical use because they could not operate effectively on the high seas or deliver "sufficient aircraft in the air at one time to insure a concentrated operation". Instead, Mitchell believed a surprise attack on the Hawaiian Islands would be conducted by land-based aircraft operating from islands in the Pacific. His report, published in 1925 as the book Winged Defense, foretold wider benefits of an investment in air power, believing it to be, at both that time and in the future, "a dominating factor in the world's development", both for national defense and economic benefit. Winged Defense sold only 4,500 copies between August 1925 and January 1926, the months surrounding the publicity of the court martial, and so Mitchell did not reach a wide audience
If you go back and read contemporary accounts, you'll find this sort of thing happens quite a bit. Perhaps the most famous of the visionaries, Nikolai Tesla, unquestionably made tremendous contributions to his field, but when it came to predicting the future of the technology, he was wrong far more often than he was right, most notably with long distance wireless transmission of power.
The problem is that when looking back at these advocates, we tend to lose sight of the specifics and conflate the wisdom of their positions with the overall impact of the technology. We retroactively change the questions being debated, often assigning the skeptics stands that no one at the time believed. "Does the future of military air power lie in long range bombing or close air support?" becomes "will air power change warfare?" To go back even further, "you can't sail from Europe to Asia because the world is much bigger than you think" becomes "you can't sail from Europe to Asia because the world is flat."
