It is by far the biggest counter-terrorism investigation mounted in Australia, involving 850 personnel from intelligence agencies and police forces across three jurisdictions.
The pivotal moment for Operation Pandanus came about six weeks ago, said the New South Wales Police counter-terrorism commander Norm Hazzard.
That is when covert surveillance by spies and police is said to have come across information that suggested the young, radical Muslims they had under their watch might be preparing to go the next disturbing level.
The intelligence is said to have suggested the men were seeking to obtain a large batch of chemicals which, mixed together, could make a powerful explosives device. The materials were almost identical to the chemicals used in the London bombings of July 7, said the NSW police commissioner, Ken Moroney.
Known as acetone peroxide, or triacetone triperoxide, the chemical concoction is a highly unstable but lethal mix made up of readily available materials.