I appeared on BBC Two's Daily Politics to outline the case for the UK's next government to commit to spending 6% of GDP on defence over the course of the next parliament. Given the limitations of airtime, there are quite a few points that I could not make at the time, and should be elaborated.

The basic case is as follows. The defence of the realm is beyond question the most important duty of any government. In the judgment of most informed opinion, the nation's non-nuclear defences are in a parlous state.

The UK, however, does not aspire to be a nation content with its own defence, but to play its role - alongside the US - in the maintenance by arms of the international order, as indicated by our valued seat on the UN Security Council. For that role, our military is not just dubiously but utterly ill-equipped, thanks to many years of funding cuts over successive governments.

As an island nation, our first line of defence is in our Royal Navy. Navies are also useful tools to have during peacetime, as they can serve on humanitarian missions, be sent off across the world to reassure allies, and fight pirates and traffickers.

It is astonishing, therefore, that the Navy is arguably in the worst shape of any of the services. The major fighting strength of the Navy lies in an underwhelming 13 frigates, six destroyers (that are troubled by propulsion problems), and 11 submarines (of which seven are attack submarines). Total ship strength is down by 20 since 2005, and 28 since 2000.

Two new aircraft carriers are under construction, and will enter service in a few years. They will have sufficient aircraft to operate effectively, but their key weakness will be a lack of protection from the rest of the shrunken fleet. The whole plan leaves absolutely no margin for error against any sort of peer enemy.

Moreover, a focus on raw ship numbers hides an even more worrying loss of technical capability. The only helicopter carrier, HMS Ocean, is going out of service with no replacement planned. The only ship-launched anti-ship missile capability our Navy possesses is the antiquated Harpoon, which is scheduled to go out of service in 2018. Staggeringly, no immediate replacement is available, or indeed is likely to be in place for another 10 years. Our frigates and destroyers will be left with only their main guns, which obviously have a far shorter range than missiles.

Our fixed-wing anti-ship missile capability is similarly non-existent. No aircraft in Navy or RAF service are effective weapons against ships, and there seem to be no plans to fix this problem. Perhaps most shockingly of all, the UK currently lacks the airborne capability to patrol its own shores against enemy submarines, and on several recent occasions has had to call upon the assistance of our allies to track hostile Russian vessels.

In both the Army and Navy, recruitment is a major issue, and both are operating below their agreed strength, despite that strength itself being remarkably low. The entire British regular Army (not including reservists) could quite comfortably fit into Wembley stadium.

The recruitment issue lies partly in a fairly strong economy, but largely in the increasingly dire pay and conditions our servicemen and women are expected to endure. The recruitment crises operates as a vicious circle; poor recruitment puts extra work on those currently serving, driving down morale, and lowering the retention rate. There is no obvious solution for this other than some straightforward above-inflation pay rises.

In an ever-more dangerous world, marked by a threatening Russia that menaces our Nato allies in Eastern Europe - to say nothing of a powder-keg Middle East - we evidently need to restore our lost capabilities. Because big-ticket items take a while to come into service, much of this spending should become upfront, and after five years spending could probably be allowed to taper off to a long-term level of 4% of GDP per year. Currently, we barely hit the Nato minimum of 2%, thanks partly to creative accounting.

It has become obvious that this is not sufficient for a country that aims to project force globally. Historically, we spent 5% of GDP throughout much of the Cold War, including during the mid-1980s. The global situation seems no less threatening now.

Evidently, this calls for a radical re-orientation of the government's tax and spending priorities. The triple lock must be abolished. Pensioner perks such as free prescriptions, free bus passes, and free TV licenses are all well and good, but our national security needs have grown so great that we can no longer afford to be so generous to a demographic that has seen unprecedented income growth over the past seven years.

The VAT base must be radically broadened, and I would suggest also that housing benefit should go altogether. Even after some generous compensatory increases to Universal Credit and the Working Tax Credit, these reforms would still very massively increase revenue. Uneconomic and eye-wateringly expensive transport schemes such as HS2 should be scrapped.

#SpendtheSix must evidently be coupled with a renewed drive for efficiency at the MoD. It is not clear that the quasi-monopoly that BAE Systems enjoys over defence contracts leads to good value for money. Whether or not it should be broken up is one of many hard questions facing our country.

Perhaps Theresa May's forthcoming vast majority in parliament will, after 8 June, embolden her to ask them.

Andrew Sabisky is an independent research worker and writer. Follow: @AndrewSabisky