In most countries - certainly rich, stable, industrialised giants - this would be a laughable absurdity. But in Japan, there is no smirking. A few weeks ago, the idea of amateur religious maniacs holding the country hostage with a Nazi nerve gas was unthinkable too. Now, mention of words like coup d'etat and revolution produces a strange reaction, more shiver than smile.
Growing evidence - filtered through the Japanese media, from anonymous sources in the police - suggests that the cult had established startling links with the Self-Defence Force (SDF), Japan's armed forces. On 19 March, the day before the sarin attack, an Aum member who was a serving sergeant in the SDF, threw a petrol bomb at the cult's headquarters in Tokyo - a carefully planned distraction, designed to throw police off the scent after the subway attack the next day. On 21 March, another Aum member in the SDF warned the cult of the imminent police raids: Aum leaders were given time to escape, carrying truck loads of incriminating evidence with them. Police have recovered a manual on protection against chemical weapons given to the cult by an SDF officer; another cultist, a former sergeant, bugged the phone of an SDF brigadier.
The SDF has always been an uneasy organisation - even down to its clumsy name. There are three SDFs - the Ground Self-Defence Force (GSDF), the Maritime Self-Defence Force (MSDF) and the Air Self-Defence Force (ASDF) - and they are, to all intents and purposes, an Army, Navy and Air Force. The combined manpower of the three is 234,000.
The reason for the fussy euphemisms is straightforward. Article Nine of Japan's constitution unambiguously states that: "land, air and sea forces, as well as other war potential, will never be maintained". The famous "Peace Constitution" was imposed by the American Occupation in 1947. Three years later the Korean War broke out and, suddenly, the prospect of an unarmed Japan on the edge of Cold War Asia became a liability. In 1952, an army was quickly mustered as the "National Police Reserve"; two years later it became the SDF.
SDF members have none of the status of their counterparts in other armies. Japan holds no military parades or fly-pasts; exercises are conducted with almost secretive discretion. For many years, membership was almost a stigma: there are stories of young women breaking off engagements on discovering that their fiances' families had SDF connections. Aum Shinri Kyo drew many of its members from marginalised, voiceless groups in Japanese society: widows, lonely teenagers, ambitious young men stranded in unbending company hierarchies. The SDF, bizarre though it sounds, falls into the same category.
It would not be the first time that attempts have been made to suborn the Japanese military. In 1936, a famous coup attempt known as 26 February narrowly failed to bring about direct military rule. In 1970 the writer Yukio Mishima disembowelled himself in a Tokyo barracks after a spectacular attempt to bring about an uprising. As recently as October 1992, a GSDF officer earned himself a swift discharge after publishing an extraordinary article in a right-wing magazine. "It is no longer possible to correct injustice through democracy," wrote Major Shinsaku Yanai. "The only means left is a revolution or coup d'etat."