National Serviceman Reg Considine said the memorial, which stands at the base of the Harold Mair Bridge, is engraved with the names of servicemen who have died.

Mr Considine said last week he'd noticed you could no longer see the memorial as you drove along Young Street but the damage wasn't discovered until he investigated on Monday.

Mr Considine said fellow 'Nashos' - who was conscripted into military service under the National Service Act and all in their 70s or 80s - were devastated.

"The poor old fellas have been pretty upset, especially as it's coming up to Anzac Day and we always have a memorial up there," he said. 

"I was disturbed as to why anyone would do it, it would have taken a hell of a lot of effort to knock over."

The Border National Serviceman group said they don't think the act was targeted, but given the weight and size of the memorial they believe multiple people must have been involved. 

"It's highly disrespectful and thoughtless," he said.

"I daresay the instigators wouldn't have thought 'let's knock it over because we don't like Nashos'. No, I think it's just a thoughtless stupid act that happened."

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Mr Considine said they were going to have to hire a crane to lift the marble memorial back onto its plinth and a stone mason to assess and repair any damage.

"Hopefully there's not going to be damage that can't be repaired before Anzac Day," he said.

Mr Considine said many people conscripted into national service have since passed away and are listed on the back of the memorial. 

He said their families were devastated by the vandalism. 

"The people that did this wouldn't be thinking of the wives and children [of the dead listed on the memorial]," he said.

Despite the disrespect and hassle caused,  Mr Considine said they don't want to vilify the vandals, but would like them to think about the consequences of their actions. 

"I just hope they reflect on it and remember what the thing represents and feel some sort of contrition about it," he said. "If they in themselves feel 'that was pretty stupid' that's all we can expect and hope for."

He said the incident had been reported to police and council. 

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