They struck overnight damaging the memorial which is only a year old.
Goodna Police are investigating the incident.
Ipswich City Council will repair the monument in time for Anzac Day on April 25.
Local Councillor Paul Tully described the vandalism as "sickening".
"There is an Ipswich City Council reward of up to $2000 for information leading to the conviction of those responsible," Cr Tully said.
Information can be passed on to Crime Stoppers on 1800 333 000.
