Even for a President as unpredictable and impetuous as Donald Trump, the assassination of Iranian general Qassem Soleimani came as an enormous shock.

While there may have been operational reasons for the lack of consultation with American allies, events have clearly caught friend and foe alike by surprise.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 2 minutes 5 seconds 2 m 5 s Iranian Revolutionary Guard missiles hitting Al Asad airbase

Deciding how to respond will be an important test for governments around the world, especially those with close strategic ties to the United States.

In this context, few countries have more enduring security ties to the United States than Australia.

Indeed, the fact that Australia has both troops on the ground in Iraq and a naval commitment in the Strait of Hormuz is a legacy of its support for the US in the strategically disastrous and ill-conceived invasion of Iraq under the leadership of George W Bush.

Two points are worth making about the Iraq War in retrospect, as they tell us something about Australia's possible policy options and their consequences in this confrontation, which has the potential to be even more consequential if events spiral out of control as they well might.

Repeating the 'epic failure' in Iraq?

First, from the perspective of Australian security and its national interest, the war in Iraq was a war of choice.

There was absolutely no need strategic for Australian forces to have taken part, and they made no difference to the outcome of the war itself or the subsequent efforts to stabilise Iraq.

Australian participation in the coalition of the willing was primarily symbolic and designed to make American actions look less unilateral.

John Howard talks with Australian soldiers in the green zone in Baghdad in 2005. Was there any strategic need for Australia forces to have been sent to Iraq?

Much the same argument could be made about Australia's continuing presence in the region.

Yet even though the numbers of personnel and assets are small, the 300 or so troops on the ground are potentially now very much in harm's way and will be considered legitimate targets by Iran's supporters in Iraq.

Indeed, one of the ironies of the Trump administration's actions has been to harden opposition to the presence of the US and its allies in Iraq, despite all the blood and treasure that has been expended there.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 19 seconds 1 m 19 s Donald Trump said no Americans were harmed in the missile strikes. (Pic: Reuters)

One might have thought that this epic failure might have made the leaders of both the US and its allies think twice about staying in a region where their presence is clearly resented and destabilising.

Indeed, Trump owed his surprise election victory in no small part to his repudiation of Barack Obama's policy in the Middle East and his promise to bring American troops home.

Yet now the world faces the possibility that America's military engagement may be radically expanded yet again, with no greater certainty about the possible outcomes in the short or long term.

What are the strategic outcomes?

The second point to make in this context, therefore, is that the history of Australian support for American actions in every major conflict the US has chosen to engage in since World War II suggests that whatever the Trump administration chooses to do on this occasion, it is likely to do so with Australia's uncritical and unequivocal support.

While other American friends and allies have expressed alarm about the unpredictable consequences of an unnecessary and potentially disastrous ratcheting up of tensions across the entire Middle East, the Morrison government has more predictably suggested that it will "work closely" with the US.

A foreign crisis will also provide a possibly not unwelcome distraction from the Morrison government's escalating domestic problems.

Whatever Australia decides, the 300 or so Australian troops on the ground in Iraq will be at the sharp end of decisions taken in Canberra and Washington.

Some may argue that this is the risk that a country's armed forces have to take to uphold national security.

There are indeed times when the national interest and direct threats to the country may make such risks acceptable, even necessary.

This conflict looks like another war of choice that was entirely avoidable, however, with no sense of long-term planning or clear strategic outcomes.

It's also important to remember that Iran's leadership had taken part in a painstakingly negotiated diplomatic agreement that held out the possibility at least of denuclearisation.

By contrast, it is difficult to see what the current policy will achieve. Not only has Iran now renounced the agreement, but its growing middle class, which might have been the best hope of overturing a repressive and anti-Western regime, has now fallen in behind its theocratic leaders.

European allies despair, but what about Australia?

Little wonder some of the US's European allies despair of America's erratic and counterproductive leadership and have moved to distance themselves or directly criticise its policies.

Nothing suggests Australia will follow suit.

On the contrary, no matter how dangerous or destabilising the Trump administration's policies prove to be, they are likely to enjoy the support of what former Prime Minister Tony Abbott described as America's "utterly reliable partner".

Even if, as seems possible, both Iran and the US don't take further military action in the short term, Australian policy will remain hostage to unpredictable events.

And it is uncertain whether Iran would be able to stop further action by its sympathisers and proxies, to which the US may feel compelled to respond.

Under such circumstances, Australia's most productive policy might be to urge restraint all around, rather than reflexively signing up for yet another conflict with no obvious benefit or conclusion.

Mark Beeson is a Professor of International Politics at the University of Western Australia.