Bradley Perrett | Missiles for the navy, air force and army: sizing up the latest defence announcements

He meant that we had to be able to hit an enemy's forces while they were still a long way from Australia, to make it hard for them to attack us. Of course he was talking about China.

So let's use that principle to assess four defence equipment acquisitions that the government announced, or re-announced, in the past week.

The one that got the most attention was for more than 200 Tomahawk strike missiles, which will be the longest-range ammunition in our inventory, able to fly at least 1850 kilometres from the ships that could launch them.

Unfortunately, the ships won't be able to launch many Tomahawks nor launch them very often. So this purchase is much less significant than it seems to be.

A strike missile is an expensive weapon that can fly a long way to hit a surface target that is too well defended or too distant to attack with bomb-carrying aircraft. The target could be a ship or a stationary land object, such as a bridge, sensor installation or air base.

Strike missiles are indeed the essence of impactful projection, so they're becoming central features of our defence policy. We're planning to operate at least nine different designs of such weapons.

But we have just three ships that can carry Tomahawks, the destroyers HMAS Hobart, Brisbane and Sydney, which are designed mainly for air defence - shooting down aircraft and missiles. They have hardly enough missile storage-and-launch cells even for that job, only 48.

A reasonable guess is that no more than eight cells on each ship could normally be allocated to Tomahawks, so it would be able to fire only a moderately-sized salvo of eight strike missiles.

And after it did? Well, if it was supposed to be available for more strike missions, it would have to return to base to load more Tomahawks. Not until after a few days, maybe more than a week, would it be back on station and ready to shoot again.

So that's a pretty mild and intermittent strike capability, one that may not even be available when and where it's needed. It depends on where the ship is, and indeed on whether that large, slow steel object, easy to see from space, is still afloat.

Far more significant, eventually, will be the air force's pending acquisition of JASSM-ER strike missiles, which the Morrison government announced last year and which the Albanese government will probably want to announce a few times, too.

Unlike ships, aircraft can provide an almost continuous and wide-ranging ability to make attacks. They can strike a target in the morning and be back to hit it again in the afternoon, or they can quickly switch to another target hundreds or thousands of kilometres away from the first.

With in-flight refuelling from tanker aircraft, fighters can reach targets just as far as any that an Australian destroyer is likely to threaten.

All that assumes, however, that the fighters and tankers can use an airfield that hasn't been smashed up by enemy strike missiles, and that the aircraft themselves haven't been wrecked on the ground. (By the way, Mr Marles, where are the plans for toughening our northern air force bases and dispersing aircraft to civilian airfields?)

The government also said this week we would buy more than 60 AARGM-ER missiles designed to attack radars. That sounds pretty obscure but is in fact rather important.

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Imagine a Chinese base on an island near enough to threaten Australia. If a war broke out, we'd need to neutralise the base, ideally with cheap bombs hurled by fighters instead of multimillion-dollar strike missiles, which would be in limited supply. But the base may be protected by air-defence batteries.

So the attackers could begin by launching AARGM-ERs, which would home in on the radio signals from the defence batteries' radars. Even if the radars shut down, the AARGM-ERs would stay on course, switching on their own little radars in the last few seconds to see the defensive equipment and destroy it.

That's a capability that China would have to think carefully about before building military installations close to us.

A third equipment acquisition will be for 22 HIMARS launcher trucks for surface-to-surface missiles, adding to an intended order for 20 such vehicles for the army that was announced in January.

HIMARS launchers are excellent, and having enough of them is important, but the main issue is what missiles they'll be used for. At first, they'll carry only weapons for ground battles, which is a low priority in defending against China.

But the government says the program is also "scoped" (whatever that means) to buy PRSM strike missiles that should be able to fly more than 500 kilometres. It seems the army proposes that in a war it would station units with PRSMs and other strike missiles on the territory of countries to our north to threaten Chinese installations and ships.

The US Army has been due to begin fielding PRSMs this year. Hopefully, we won't be far behind.

The other acquisition plan in the latest announcements is for army battlefield weapons, little Spike LR2 missiles for destroying tanks or other armoured vehicles a few kilometres away. While they're important for land combat - to the extent we need to be ready for it - they have little to do with impactful projection.