Salute!
We may have some Aussies here that flew in 'nam those early years, and they can add to my comment. Her Majesty would not allow our Brit exchange pilots to deploy with us when our unit went there.
My first tour in 67/68 had almost zero "traffic control". The CRC's ( combat/control reporting center - Paddy, Peacock, Paris, Pyramid, etc.) provided advisories and tracked us if we used a specific squawk. We would get with the nearest one and tell them our mission number, planned altitude and provide altitude updates, but mostly did our own navigation. They could help, but we did most of it. The CRC would advise us of altitude and route conflicts, but nothing like stateside ATC at the time. They also coordinated with approach control and the control agency or whatever at our destination/target.
There was virtually no civilian traffic except a few airliners at the big airfields.
They had good connections with the military command centers and would coordinate changes to our mission, plus tell fields we were inbound with an emergency or fuel divert. Think "real" ATC type control.
By the end of 1972 we were getting to "ATC" type stuff with the CRC's- assigned altitudes and such. If not on a combat mission we had to file an ICAO flight plan at the tower.
By 1975 on my last tour it was like stateside, with training areas and low level routes and so forth.
Oh well, we innovated, improvised and overcame. But the early years required good airmanship and DIY approaches on many occasions.
Gums recalls...