Sir Arthur Tange, the equally obnoxious and talented bureaucrat (who in the 1970s, with a seemingly single-minded determination to crush the military's top brass, created the current defence structure) understood money. He knew it was the key to seizing control of Defence. As head of the nascent Defence Department, he looked on as the service chiefs squabbled, demanding more and better equipment. Tange had the wit to understand that they all, instinctively, believed that only their service could defend the country. Each pulled their own separate way, plumping for ships, tanks, or fast jet fighters. Tange reasoned the only way to make sense of these competing demands was to find a single measure that would allow them to be directly compared.

He discovered it: money.

He forced the chiefs to compete amongst themselves by insisting the funding envelope was fixed - only equipment was fungible. He demanded they serve up a joint shopping list. If the forces wanted a new aircraft carrier, that was fine - but they'd have to pay for it by giving up another bit of equipment somewhere else. That's why, after the Falklands War when the British reneged on selling us one of their flagships cheaply and it became obvious there would have to be cuts elsewhere, the (previously) urgent need for a replacement vessel suddenly disappeared. The navy couldn't persuade the other services the requirement was really vital, and - despite doomsayers at the time - we've gotten along quite nicely without one ever since.

Tange's fixed-budget strategy is a stricture Defence Minister Richard Marles would do well to adopt.

Last week Peter Dutton claimed that before his party lost the election, he had a cunning plan to seize two US nuclear-powered general-purpose attack submarines (SSNs) as they rolled off the slipway and sail them, half-crewed, to operate with our navy. All that was missing from this extravagant claim was the detail. If it was such a bargain, why didn't he grab it while he could?

The reason he didn't becomes clearer when you examine the proposal more closely.

The Royal Australian Navy would have acquired end-of-class boats, rather than new ones, and the deal would have come at enormous cost. Australia would have been effectively subsidising the establishment of a third American shipyard to build extra boats for the US Navy. The vessels would also have initially been required to be commanded and crewed by foreign sailors, until ours could be qualified to work on the nuclear boats.

Would'a, could'a, should'a. The reason Dutton never persuaded his colleagues that this was a workable option is simple: it wasn't.

Where was the money to pay for this deal coming from? Whose strategy did the subs fit into? Attack submarines don't carry nuclear missiles, and only make any sense in terms of a conventional naval war against China off Taiwan. Is Dutton still offering security guarantees to Taipei? Even Scott Morrison told him not to do that.

The reason the idea is rubbish is Tange's immutable law. Remember: you can have whatever you want, but the funding envelope remains the same. Sure, this country can afford SSNs. The problem is what needs to be given up in order to do so.

The navy's already bleeding as it searches for money to pay for future frigates. The army wants hundreds of new heavy armoured vehicles. The air force is committed to new fighter jets, but urgently requires un-piloted platforms as well. The last government established a Space Force, and fighting cyber wars is essential. A missile force is becoming vital. The cost of operating the forces is already soaring, and this extra burden would send it through the stratosphere.

There is, of course, an easy way to fix the problem: a non-negotiable, inflation-linked $2000 levy on every taxpayer. This would (very roughly) add 1 percent of GDP to our defence spend, and would provide the sort of money needed to pay for the multiplicity of these "much needed" long-term equipment projects, the immediate additions to capability, and the people to operate them once they're obtained. But let's get real about the cost. Without a specific commitment to raise taxes, there's no money for such a questionable and extravagant spending program.

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The other question is how long such submarines would remain viable.

Two years ago, an expert panel at the ANU's National Security College insisted that in less than 30 years new detection technologies will mean the world's oceans will in effect be transparent. Submarines will become vulnerable, the hunted instead of the hunters. Instead of prowling the waters, they will be hiding and attempting to avoid detection, because once found they'll be destroyed by small autonomous torpedoes. Specially tuned blue-green lasers can already penetrate seawater, "pinging" subs, and the vessels can't hide deep without their hulls being crushed by pressure. The capacity of robotic underwater vehicles is zooming ahead. Soon they'll carry out all the missions assigned to SSNs. The idea that buying a couple of US submarines is some sort of silver bullet is farcical, even without considering the opportunity cost of these vessels.

We need to do what Tange demanded: return to first principles. For every proposed purchase, we must ask: What is the strategic bottom line, and how much will it cost? Why send money overseas to buy soon-to-be-obsolete submarines, when we could foster a vibrant sovereign Australian missile industry for the future? Why chain ourselves to the expensive, outmoded and inadequate past, when we could be developing our own world-leading technology and achieve exactly the same objective?

Tange wasn't liked. He didn't possess much imagination. His rule, however, ensured Defence's budget provided value for money.

Marles needs to apply a similar rubric.