High over northern Iraq, a crewman in an RAAF Super Hornet was viewing an Islamic State fighter on the aircraft's sophisticated night vision camera when the man suddenly vanished.
He had disappeared into a well-concealed cave complex in the side of a hill.
And that was the genesis of a major air raid by Australian and coalition aircraft, launched within 24-hours of the initial sighting.
RAAF director general of air operations Air Commodore Joe Iervasi said some coalition partners could use "bunker buster" bombs designed to penetrate deep underground.
Bombs dropped from Australian aircraft could be aimed into a tunnel entrance, he said.
Chief of joint operation Vice Admiral David Johnston said the raid involved 20 Australian and coalition aircraft plus Kurdish security forces on the ground.
Subsequent reports indicated more than 100 IS fighters were killed in the clearance operations.
In another mission, an Australian Super Hornet crew led an attack against an IS bomb factory in the city of Mosul.
"This was a highly complex mission with the target being within a multi-building compound located within a densely populated area of Mosul and involved attacks on 34 targets," he said.
Air Commodore Iervasi said that before a strike of this level of complexity, there was extensive surveillance to assess who was present and to minimise civilian casualties.
"Leading up to that particular strike, the pattern of life indicated it was ISIL moving in and around those facilities. It was highly unlikely there were non-ISIL in the vicinity," he said, using another name for IS.
The raid was apparently successful, producing a number of secondary explosions.
In the last three weeks, Australian aircraft dropped bombs 20 times, making a total of 47 such raids since the start of strike operations on October 5.
Vice Admiral Johnston said the Australian special operation task group had now deployed into Baghdad and had begun working with members of the Iraqi counter-terrorism service.
At this stage they are working in the Baghdad diplomatic security centre near the Baghdad international airport, assisting with co-ordinating close air support.
"We are making preparations as required to go forward to forward operating bases," he said.
