In 2017 Cafferkey was in Syria providing medical aid before he joined the People's Defense Units, an arm of the Syrian Democratic Forces aligned with Rojava, and fought against the Islamic State.

Politically, Cafferkey was an Irish Republican and socialist[4][5] who was a part of the Shell to Sea campaign which occurred in the late 2000s and early 2010s.

The Irish Times has stated that Cafferkey had been in Ukraine for roughly a year before his death, and that he had been working mainly with anarchist-aligned aid groups.

[12] Solidarity Collectives, a Ukrainian left-wing anti-authoritarian network, reported that he was delivering humanitarian aid and cars for frontline zones from Poland to Ukraine.

[6][14] Some reports have indicated that Cafferkey died fighting alongside Russian anarchist Dmitry Petrov (a founder of the Combat Organization of Anarcho-Communists) and US citizen Andrew "Harris" Cooper (a former US Marine and left-wing organiser), in a battle for a vital supply road near Bakhmut.

Amongst those tributes were some from Tánaiste and Minister for both Foreign Affairs and Defence Micheál Martin, who stated "My deepest sympathies to the Cafferky family on the sad passing of Finbar.

It has been the Government and media who have been promoting anti-Russian propaganda, distorting the truth about the conflict in Ukraine, misleading people like Finbar Cafferkey.

We also do not know if Mr. Martin’s remarks signify support for the Irish to take part in combat in Ukraine, but we do know that if that is the case, then Ireland would be the direct participant of the conflict with all the ensuing consequences.

He stood against all forms of imperialism, be it US, British, or Russian, and was strongly opposed to Ireland's support of US troops and any moves toward joining NATO.