This time it has been described as a "modest, meaningful and time-limited" contribution. Our initial commitment is a frigate, surveillance aircraft and personnel. The UK and Bahrain are the only others to join this "coalition" at this stage.

This is against the background of us joining GW Bush's illegal invasion of Iraq, and then in the war in Afghanistan, which cost us billions, and is still costing in terms of having to deal with the continuing psychological and physical consequences for many of our military personnel, as well as the unnecessary loss of life and serious injury.

In each case our commitment has had more to do with Australian leaders seeking to ingratiate themselves with the US President of the day, rather than on hard evidence of a threat (recall that there were no weapons of mass destruction), or genuine national interest.

In each case the contribution started as "modest" only to increase in significance, especially as the US continued to change its justification for being involved on each occasion - what can be called "mission drift".

Remember the post 9/11 justification for the US invasion was "to get Al-Qaeda" which soon drifted, and expanded, to "regime change".

On this occasion, our government has been warned that the involvement of our military in the region, in the absence of any credible threat to Australia, could be seen as an "act of aggression", and as such in breach of international law.

Scott Morrison has said, in defence of the decision, that the "destabilising behaviour" in the Gulf was a threat to Australian interests, particularly our enduring interest in the security of global sea lanes. Defence Minister Linda Reynolds has said, "Australia's core interest in the mission is de-escalation".

How do we define "destabilising behaviour"? It can't be limited to the recent Iranian seizure of two oil tankers. The "brinkmanship" must be traced back to Trump's withdrawal from the Iran nuclear deal in May 2018, and the considerable evidence since that he was "itching" for a military confrontation with Iran.

As usual his comments/tweets and initiatives have come and gone as he has attempted to impose a "maximum pressure" strategy on Tehran.

His "emboldened" Israel is also always looking for an opportunity to strike, in some way, against Iran.

So, the real question for us, as a nation, is "Do we really want to be part of all this, and particularly of where it might end up", driven as it is by an extremely volatile and unpredictable Trump, in a region that is a geo-political tinderbox?

Don't we have other, more significant, priorities? I would suggest that we do!

Shouldn't we be more concerned by Chinese aggression in the South China Sea, in seizing disputed territories and quickly turning them into a military base, with possible future impacts on freedom of navigation and fly-over rights?

Shouldn't we be challenging the US to join a "coalition" in this area of much greater concern to our national interest?

Or, what about recognising just how much we are lagging Chinese influence in the South Pacific, and just how little we will achieve with our infrastructure fund, and our recent "donation" to assist these nations with climate change?

Might I suggest that Morrison et al take a hard look at what the Chinese have already achieved in Vanuatu?

A friend who has maintained a home there for years, challenges us to look at the construction of the Chinese Embassy, and the Convention Centre - more like a potential military headquarters/base - and to see the 100-plus warehouses built but sitting empty, or recognise how the Chinese are buying any property with water!

Our leaders and ministers are all too easily "smooched" by a Bush, or a Trump, or a Pompeo, to dress up these commitments, that basically end up open-ended, as "in our national interest", when any sober assessment would suggest that they are not, and that we have other more pressing priorities.

John Hewson is a professor at the Crawford School of Public Policy, ANU, and a former Liberal opposition leader.