First, national defence is “the quintessential public good” in that the taxpayers who pay for “national security” compose a diffuse interest group, while those who profit from it form concentrated interests. This calls into question the assumption that American national security is directly proportional to its military spending (America spends more on defence than most of the rest of the world combined).
Second, the public is ignorant of foreign affairs, so those who control the flow of information have excess influence. Even politicians and bureaucrats are ignorant, for example most(!) counterterrorism officials — the chief of the FBI’s national security branch and a seven-term congressman then serving as the vice chairman of a House intelligence subcommittee, did not know the difference between Sunnis and Shiites. The same favoured interests exert influence at all levels of society, including at the top, for example intelligence agencies are discounted if they contradict what leaders think they know through personal contacts and publicly available material, as was the case in the run-up to the Iraq War.
Third, unlike policy areas like education, it is legitimate for governments to declare certain foreign affairs information to be classified i.e. the public has no right to know. Top officials leaking classified information to the press is normal practice, so they can be extremely selective in manipulating public knowledge.
Fourth, it’s difficult to know who possesses genuine expertise, so foreign policy discourse is prone to capture by special interests. History runs only once — the cause and effect in foreign policy are hard to generalise into measurable forecasts; as demonstrated by Tetlock’s superforecasters, geopolitical experts are worse than informed laymen at predicting world events. Unlike those who have fought the tobacco companies that denied the harms of smoking, or oil companies that denied global warming, the opponents of interventionists may never be able to muster evidence clear enough to win against those in power with special interests backing.
Hanania’s special interest groups are the usual suspects: government contractors (weapons manufacturers [1]), the national security establishment (the Pentagon [2]), and foreign governments [3] (not limited to electoral intervention).
What doesn’t have comparable influence is business interests as argued by IR theorists. Unlike weapons manufacturers, other business interests have to overcome the collective action problem, especially when some businesses benefit from protectionism.