On Thursday, the Solomon Islands confirmed it would sign a security pact between with China. A leaked draft of the deal had already shown what we could expect: China might use it to set up a military installation in the Solomons.

Two days before, the Australian budget recommitted to funding the plans of a 2016 defence white paper that was obsolete when it was written, failing to properly face a Chinese threat that by then had been obvious for years.

It's a crying shame that we have to discuss defence policy in relation to one of the little South Pacific neighbours that Australia has long sought to help. But we're forced into it, and almost certainly will be again.

These countries are not colonies and the South Pacific is not our empire. Their governments will do as they wish, and not always for the right reasons.

In general, South Pacific countries have what diplomats like to call "weak institutions". Expressed more bluntly, it means many politicians and officials in them are corrupt (though this does not mean that Solomons Prime Minister Manasseh Sogavare is). Whereas we must not pay bribes or support some groups in politics against others, China is happy to do it.

It will also order its companies to build up local economic presence and therefore influence, whether they make money or not. And it can construct popular but unaffordable infrastructure that corrupt governments agree to pay for later, the debt becoming a trap that keeps the country under Chinese influence.

We must try harder to counter China in the South Pacific, but experts on the region have no sure-fire ways of doing it. So we had better get used to the idea of the great power of East Asia moving into our Pacific flank.

China may pick up the Solomon Islands this time, and in a few years get a deal to set up a base on another island nation that stands on or near the line from the US through which we might want wartime supplies.

The big prize is Papua New Guinea, and there have already been moves to establish a Chinese port-city there, on the south coast just 200km from Cape York.

A question arises: why does China want a base in so far-away a place as the Solomon Islands?

Unlike the US in such countries as South Korea and Germany, China in the Solomons is not trying to protect a friend from a dangerous neighbour. But maybe, more like the US in the Persian Gulf, where it watches Iran, China would like to be within convenient reach of a possible enemy.

That would be Australia.

The Solomons' most most southwesterly territory, Rennell Island, is not much more than 1500 kilometres from Queensland. The national capital, Honiara, is 1800-2300 kilometres from our most important defence installations in the state - distances that cruise and ballistic missiles can cover.

Anti-ship missiles in the Solomons could threaten naval and civilian movements in the Coral Sea and South Pacific, while air-defence batteries targeted anything in the skies close to the islands.

Such weapons do not have to be kept permanently at a base in the Solomons. They could be suddenly flown in during a time of tension, along with the small number of soldiers needed to ensure that the local authorities could not interfere. It wouldn't matter that the base was supposed to be only for ships.

The base could hardly be supplied in wartime, because it would be so far from China, so it would probably whither as it expended its weapons. But Australia would have to guard against those weapons until they were used, or divert forces, mainly air power, to get rid of them.

MORE AGE OF THE DRAGON:

So the prospect of China having this base greatly complicates our defences.

But never fear; Peter Dutton is here. The defence minister is a man with a plan, and he's sticking to it.

It's not his plan; it's Marise Payne's plan, made in 2016 when she was defence minister. But it might as well be Robert Hill's plan, made in 2003 when he was in the job and our main concerns were Iraq and Afghanistan, while China was weak.

Dutton works so hard with Scott Morrison to create the atmosphere of a khaki election, and to promote the idea that the Coalition is strong on defence, but he lets his department and the armed services carry on largely as though we were still living in the unthreatening world of the early 21st century.

This week's budget provided for defence spending rising at a robust average of 5.6% a year up to 2025-26. This will fund the 2016 plan, as (slightly) amended in 2020, the government says.

We should be going hell for leather in trying to reinforce our air and sea power, but, under the plan, most near-term additions to our defence capabilities would be useful for land wars - just like those that were on our minds in 2003.

So in the next few years Dutton's plan will give us attack helicopters good for hitting nearby ground forces, along with propeller-driven drones that can't survive against enemies that can shoot back. And, of course, there are those incredibly expensive and doubtfully useful infantry fighting vehicles, plus tanks and artillery - none of which can swim to the Solomon Islands.

Think about that during the imminent election campaign, when Morrison and Dutton will keep telling you that, unlike Labor, they take national security seriously.