The United States is quietly building up its forces in striking range of Iran.
B-1B bombers have arrived in the desert kingdom of Saudi Arabia, along with stealth fighters, missile batteries and specialist troops.
Exactly why they're there depends on who you listen to.
Everything changed when, on September 14, wave after wave of cruise missiles and drones burst among Saudi Arabian oil facilities. Shockwaves rippled around the world.
According to international intelligence agencies, the brazen strikes came from Iranian soil. But few have openly come out and accused the Government in Tehran of being behind them.
Iran insists it has had nothing to do with raids on oil tankers or the bombing of Saudi Arabia. But claims that Yemeni Houthi rebels were responsible have been dismissed as implausible.
It's a classic example of modern grey warfare, where even implausible deniability shields rogue nations from international consequences.
Nobody wants a war with Iran.
It would be a complicated and expensive conflict.
But does Tehran see the lack of response as a sign of weakness to be exploited?
Or is Saudi Arabia already applying similar grey tactics in response?
News of explosions tearing through an Iranian oil tanker in the Red Sea earlier this month is just the latest incident in what appears to be a slowly but relentlessly escalating confrontation.
"From the first day I entered the political arena, I made it clear that I did not want to fight these endless, senseless wars," US President Donald Trump has said.
Now, the US is quietly assembling a formidable strike force capable of devastating targets deep within Iran.
AIR EXPEDITIONARY WING
The spearhead of this new US force has just landed in Saudi Arabia — an unspecified number of B-1B strategic bombers. It is the first time the big, distinctive swing-wing aircraft have deployed to the kingdom. And given their limited numbers, their appearance is significant.
The US Pentagon announced its intention to deploy what it calls an Air Expeditionary Wing at Prince Sultan Air Base in Saudi Arabia earlier this month.
This is unusual. The US already maintains a heavy bomber and strike fighter force at Qatar's Al Udeid air force base.
But Prince Sultan Air Base is 300km inland of the Persian Gulf. It's also deep inside Saudi Arabia, which may need some political attention after the embarrassing failure of its US-built technology to defend its oil facilities last month.
According to US Central Command, accompanying the bombers are two fighter squadrons, two Patriot air-defence missile batteries and one Terminal High-Altitude Air Defence (THAAD) battery.
This represents a formidable increase in US firepower.
"Taken together with other deployments, this constitutes an additional 3000 forces that have been extended or authorised within the last month," a Pentagon statement reads.
But the additional weapons and soldiers aren't the full story.
An air expeditionary wing puts in place the command structure, communications networks, support facilities and expertise capable of supporting a rapid force expansion.
The US bombers will join Australia's recently arrived P-8 Poseidon surveillance aircraft in patrolling the Persian Gulf.
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They're there to be seen. They're there to keep tabs on movements by Iran's Islamic Revolutionary Guard. They're there to respond, if necessary.
Mr Trump has been adamant that he wants to withdraw his troops from the Middle East.
But even as he pulls forces out of Syria, he's sending more to Saudi Arabia.
"The relationship has been very good," Trump explained. "And they buy hundreds of billions of dollars' worth of merchandise from us, not only military equipment. In military equipment, about $110 billion. It's millions of jobs.
"Now, with that being said, we are sending troops and other things to the Middle East to help Saudi Arabia. But are you ready? Saudi Arabia, at my request, has agreed to pay us for everything we're doing."
The additional 3000 troops are due to arrive in the kingdom in the coming weeks. This will bring the total extra deployed to the region to 14,000 since May.
US Pentagon spokesman Jonathan Hoffman said the forces were "an investment into regional security".
"As we have stated, the United States does not seek conflict with the Iranian regime, but we will retain a robust military capability in the region that is ready to respond to any crisis and will defend US forces and interests in the region," he said in a statement.
But the US and its allies are not the only ones beating the drums of war in the gulf.
State-run media in Iran has announced the country will soon be conducting naval exercises in the Gulf of Oman with Russia and China.
Moscow has confirmed the naval manoeuvres. "We, the People's Republic of China, and Iran are preparing naval drills for fighting terrorists and pirates in this part of the Indian Ocean," Russia's Foreign Minister Sergey Lavrov said.
AGE SHALL WEARY THEM
In April last year, two B-1Bs fired volleys of air-to-surface missiles against ammunition dumps inside Syria. It was a high-profile message to President Bashar al-Assad on the consequences of using chemical weapons.
The Lancer has been a familiar sight over Iraq and Syria in recent decades. But that extended deployment has worn the ageing aircraft out.
"We overextended the B-1s," air force General Timothy Ray recently told media. He was referring to a stand-down of the entire force last year for comprehensive inspections after one bomber was forced to make an emergency landing with an engine fire and faulty ejection seats.
"The wear and tear on the crews, the maintainers, and certainly the aeroplane, that was my cause for asking for us to get out of the
CENTCOM fight," he said. The US air force had been planning to begin a wind-down of the tired old bomber this year, with a phase-out date of 2036.
Now, the Pentagon appears backed into a corner. It has to find the money – and means – of keeping the Cold War veterans in the air until the next-generation B-21 Raider stealth bomber begins rolling off the production lines in significant numbers.
US Congress allocated $US1.26 billion for just that purpose in July. But the new deployment to Saudi Arabia may mean the Lancer has even more hard work ahead.
The Cold War-era B-1 Lancer bombers were initially designed to fly at supersonic speeds, skimming the ground beneath Soviet radars and missiles. Since then they have evolved into high-altitude precision-strike aircraft, reliant upon electronic warfare and supporting aircraft to blast a clear corridor through enemy defences.
They're big. They're fast. They're old.
Keeping the 40-year-old bombers flying is proving to be an expensive challenge. Out of a total of 62 aircraft in the fleet, only six were "ready to deploy" in an August review.
Since then, they've reportedly achieved a 52 per cent readiness rate.
The 20 B-2 Spirit stealth bombers in service are themselves now 30 years old and facing a raft of expensive maintenance issues. About 61 per cent of the force is operational.
Ironically, an even older aircraft – the 1950s era B-52 Stratofortress – is set to remain in the air longer than both of them. This is based on pure economics: The ancient airframe is simpler and therefore easier to maintain. It's also why they remain the best performing bomber in the fleet – with 69 per cent of the 75 aircraft in combat condition and expectations to keep them on the front line until the 2050s.
And yet, the B-1B Lancer remains the deployed backbone of the US heavy bomber force.