A former head of the Royal Marines himself, Magowan said the commandos were engaged in "discreet operations" and carried out tasks in a "hugely sensitive environment."
"In January this year, 45 Commando Group [was] deployed [on] short notice – from the depths of a dark, north Norwegian winter, to evacuate the British Embassy in Kyiv to Poland," he said in a statement published by the Globe and Laurel, the official magazine of the Royal Marines.
"Then in April, they returned into the country to re-establish the diplomatic mission, providing protection to critical personnel. During both phases, the commandos supported other discreet operations in a hugely sensitive environment and with a high level of political and military risk." (Related: Russia claims it will present 'evidence' that UK special forces were behind attacks in Crimea.)
A spokesperson for the Royal Navy told the Daily Mail that Royal Marines were indeed "deployed in Ukraine to support the U.K.'s diplomatic presence in the country," but clarified that "they served no combat function."
Magowan is the first senior military official to confirm that British marines were sent to Ukraine amid the Russia-Ukraine war. (Related: After almost 80 years, US deploys "Screaming Eagles" Division for Ukrainian front missions.)
The British Ministry of Defense (MOD) said a small brigade of British military personnel had been sent to Ukraine Prior to the onset of the Russia-Ukraine war on Feb. 24.
"British military personnel have been deployed to support discussions around the significant training being offered to the Armed Forces of Ukraine by the United Kingdom," said the MOD in a statement.
Later reports confirmed the ministry's remarks, pointing out that British military personnel alongside operators from the Special Air Service had only been deployed to supply weapons systems training to Ukrainian troops.
The Royal Marines' 45 Commando Group was involved in the battle for Port Stanley during the Falklands War 40 years ago, as well as the conflicts in Iraq and Afghanistan.
Members of the group are experts in Arctic warfare. They were sent on a training exercise in Norway, before being deployed to Ukraine to conduct quick evacuations of embassy personnel just before the war.
But Magowan's admission suggests that members of Royal Marines returned to Kyiv just a month after the exercises to perform covert operations. "Alongside wider defense, we have been heavily involved in training hundreds of Ukrainian military personnel throughout this summer. We are also planning to train Ukraine Marines," he said.
According to reports, up to 10,000 Ukrainians will be given training by the U.K. Armed Forces over the coming months.
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Watch this video that talks about the Royal Marines' covert missions in Ukraine.
This video is from the Andrew Zebrun III channel on Brighteon.com.