Sergeant Jack Tredrea wondered just what he was getting into when, as he prepared to infiltrate Borneo, he was offered a cyanide pill.

It was in event of capture by Japanese forces and the certainty of torture and execution.

The former member of Z Special Unit, the top-secret commando organization recruited during World War II to fight behind enemy lines, said he signed up “maybe because of the word ‘special'”.

“We didn’t know what it was and what we were in for. But we were young and wanted to get into it so we volunteered,” he told AAP.

He parachuted into Borneo in March 1945, leading a group of tribesmen in attacks on Japanese forces.

“They were wonderful people, believe me. From day one they welcomed us with open arms. They hated the Japanese,” he said.

From the third week in May 1945 until October it was all ambushes, he recalled.

“At that time our navy had stopped the Japanese boats bringing them any supplies so they were sending 20-30 people on patrols into various parts of Borneo, taking all the natives’ rice. We’d know 24 hours in advance which track they would be coming in on and we’d just take care of them.”