Unfortunately, the waters surrounding our shores no longer provide the assured sanctuary we've enjoyed since the end of World War II.

Now, we are confronted by asymmetric dangers, which Foreign Minister Penny Wong recently described as "grey zone threats."

The seas that have girted Australia with protection are no longer a barrier against attack.

Today, more than any time in the history of our nation, an assault on our homeland is not merely a possibility - it's an inevitable reality.

These grey zone threats are driven by technological advances in weaponry and intelligence surveillance systems that have never been witnessed before.

As such, it necessitates that government abandon its long-held conviction that Australia is immune to long-range intercontinental air and ballistic missile attacks and begin developing a whole-of-government strategy that encompasses a comprehensive and integrated defence of the homeland.

From Russia's use of cyber, drone and hypersonic weapons in Ukraine; to China assessing a low earth orbital bombardment system; to North Korea and Iran launching militarised satellites - neoteric advancements have changed the threats to our homeland.

It's those threats that should define Australia's national security mindset and the capabilities it needs to defend the homeland. It requires a mindset where Australians and government view our homeland not as mere borders to protect, but as an operational area to defend - now - not in 2035 and beyond.

The lessons from Ukraine and the Middle East, coupled with the numerous incursions into Taiwan, the South China Sea, and the Sea of Japan (East Sea) in recent months make it clear, stealth and the speed of air, missile, drone, and electronic warfare attacks are intensifying in range, lethality, complexity, and frequency.

Defence of the Australian homeland requires that Home Affairs and Defence work together - jointly - in developing and deploying a multi-domain air, maritime, and missile defence ISR network that will provide accurate indications and timely warning of impending attacks.

Working jointly, would also assist Parliament when considering budget estimates from both departments.

Currently, instead of seeking what should be whole-of-government solutions, Parliament must resolve funding requests from Home Affairs and Defence independently verse approaching defence of the homeland as a consolidated budget request based on joint capabilities and joint operational requirements.

Additionally, these grey zone threats dictate that Australia develop a consortium of common, versatile, and flexible deterrence capabilities that can defend critical infrastructures and project power in times of crisis.

Most importantly, it requires the establishment of a Home Affairs and Defence joint command-and-control architecture - similar to the US's North American Aerospace Defence Command (NORAD) - for monitoring and enabling scalable and conventional response options for government to apply from peacetime to hostilities.

The long-held belief that a catastrophic strike in Australia would be part of a greater strategic nuclear attack against a western ally or a full-scale assault on our top end by a foe is archaic.

Our adversaries are capable, now, of conducting limited air and ballistic missile attacks, or full-scale cyber and electronic warfare assaults on critical assets that could impede our ability to muster and deploy forces or support domestic or regional operations.

There is a growing consensus among AUKUS and Five-Eyes strategists that "business as usual" to national security and homeland defence is no longer sufficient.

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As national security and domestic threats converge, it is becoming increasingly clear that the tasks Australians expect of its homeland and defence capabilities far exceed the means that are available to accomplish those tasks.

Reversing this spectacle calls for a coordinated and sustained effort by Parliament, Home Affairs and Defence, in concert with our allies, to modify those essential elements of Australia's homeland defence and intelligence capabilities to identify, deter and defend against these intercontinental grey zone threats.

In the dynamic global security environment that challenges us today, Australia's conventional and grey zone threats are becoming increasingly acute.

For Parliament to simply view military operations as the sole domain of Defence, and border and critical infrastructure protection as the sole purview of Home Affairs, forsakes Australia's "golden soil ... abound in nature's gifts of beauty rich and rare," to hostile incursions and attacks.