First envisioned in the 1960s, the US Air Force's B-1 Lancer has evolved over the years to tackle the changing face of warfare.

The B-1B is a supersonic variable-sweep wing, heavy bomber that was once feared by the Soviets.

The powerful, long-range bomber's initial model, the Cold War-era B-1A, was designed to fly at high speeds and high altitudes to breach Soviet missile defenses.

But the advent of new Soviet surface-to-air missile systems prompted a re-design of the B-1A into the stealthier B-1B, capable of flying at night and in low altitudes to skirt around sophisticated air defense systems, albeit more slowly than the B-1A.

Both were capable of carrying huge amounts of ordnance, including nuclear weaponry.

"Because of its ability to rapidly deliver massive quantities of weapons against any adversary in the world, the capabilities of America's B-1B Lancer may have once been feared by the former Soviet Union during the Cold War," according to the Air Force.

The B-1B was removed from its nuclear mission in 1994 under the initial Strategic Arms Reduction Treaty between Russia and the United States, according to the US Air Force -- a treaty intended to place verifiable limits on intercontinental ballistic missiles, deployed submarine-launched ballistic missiles and deployed heavy bombers equipped for nuclear armaments, according to the US State Department.

In 1995, Russian observers were allowed to certify that the US Air Force B-1B Lancer had been removed from its nuclear mission.

After that, the aircraft would later be redesigned as a conventional bomber with a massive payload of 33,566kg.

The B-1B was first deployed in combat in Iraq in 1998 and would later function as the backbone of US close air support and strike missions over Afghanistan and Iraq.

"What I loved about the B-1 was that it had such incredible payload capacity and such incredible time on station," Jeffrey Pickler, the fire support officer for the 2nd Battalion, 503rd Infantry Regiment, told the Washington Post in 2015.

"We dropped over a million pounds [453,592.4kg] of Air Force bombs, and a lot of that was B-1s."

A continuing odyssey

Although its mission has changed over the years, the Lancer is still a formidable aircraft that has been called the most dangerous supersonic bomber on Earth.

On February 2, B-1B bombers led air strikes across Iraq and Syria in retaliation for a drone attack that killed three US soldiers at a base in Jordan.

The air strikes against Iran's Islamic Revolutionary Guards Corps (IRGC) Quds Force and linked militia groups were carried out by aircraft including long-range bombers flown from the United States, according to a statement by US Central Command (CENTCOM).

The bombers deployed 125 precision munitions against more than 85 targets that included "command and control operations centers, intelligence centers, rockets, and missiles, and unmanned aerial vehicle storages, and logistics and munition supply chain facilities of militia groups and their IRGC sponsors who facilitated attacks against US and Coalition forces," CENTCOM said.

The B-1B bomber has low-observability features including a radar cross section of 10 square meters, according to GlobalSecurity.org -- much smaller than the 100-square meter radar cross section of its predecessor aircraft, the B-52.

Designed with blended contours and radar-absorbing materials, the aircraft is much more difficult to detect than the B-52.

And with the ability to fly at low altitudes, the B-1 was designed to penetrate radar-guided air defenses. With its wings swept fully back, the B-1B can fly as low as 61 meters above the ground.

"The B-1B's role in America's military arsenal has been more of an odyssey than others," the National Interest reported in March.

"From nuclear bomber to missile carrier, the supersonic bomber has been flexible enough to adapt to a changing strategic environment, embracing new roles as necessary."