Australian soldiers departing Darwin to help train Ukrainian troops will help keep the embattled nation in the fight, as Kyiv continues to repel Russia's invasion.
Up to 70 Australian personnel will join partner nations in Britain to help boost the infantry tactics and military skills of Ukrainians.
No Australian troops will enter Ukraine.
The United Kingdom-led program is aiming to train up to 20,000 Ukrainian soldiers this year.
Lieutenant Colonel Chris Gilmore said the training was about making sure troops had the best chance of surviving on the battlefield.
They will then be taught how to fight in different terrains, including urban, woods and forests.
The 5RAR commanding officer said the Australian soldiers were incredibly proud to be given the opportunity to participate in this mission.
"They are professional soldiers, they know that this is a part of the job and they will go do it with the absolute best of their ability," he told ABC TV.
Defence Minister Richard Marles said the training formed part of Australia's enduring commitment to Ukraine.
"Training, therefore, we saw as being one of the real needs that Ukraine has," he told ABC radio.
"This is very much a reservist force now Ukraine is putting into the battlefield. It's a citizen army. It's people who are giving up their everyday jobs in order to fight.
"The heart is there. The skills ... are going to be really important to equip them for the battlefield, to keep them in the fight, to help save their lives."
Prime Minister Anthony Albanese said he would continue to engage with Ukraine on its military needs.
Australia has provided about $655 million in support for Ukraine, including $475 million in military assistance. It includes a total of 90 Bushmasters armoured vehicles.
"We are already making a substantial contribution. We will continue to engage with requests from President Zelenskiy and the Ukrainian government," Mr Albanese said.
Opposition Leader Peter Dutton said Australia had to continue to stand side-by-side with nations that shared its values.
"We need to stand shoulder to shoulder with those friends because if we do that in their time of need, they will come to our aid in our time of need," he said.
The Australian Strategic Policy Institute's Malcolm Davis said Western democracies needed to start considering supplying tanks and long-range firepower, including attack missiles.
"The worst thing that the Western democracies could do would be to drop the ball in this regard and then leave Ukraine exposed to looming Russian offences," he told ABC TV.
The personnel were formally farewelled in Darwin on Wednesday.