Engaging in extreme activism in support of others’ political struggles: The role of politically motivated fusion with out-groups

The paper, in plain language

From the Spanish Civil War to Rojava

History keeps producing people who join other groups' struggles — tens of thousands of foreign volunteers in the Spanish Civil War, Westerners fighting ISIS alongside the Kurdish YPG. Identity-fusion theory explains extreme sacrifice through a visceral oneness with one's own group; with Lotte Thomsen, Milan Obaidi, Sasha Kimel, Maor Shani and Beate Boos, I asked whether that oneness can form across ethnic lines — and what political ingredient makes it form.

Oppression is the trigger

In American and Norwegian samples, leftists fused with Palestinians — the group whose treatment their ideology frames as asymmetric oppression — but not with Kurds, until an experiment reframed the Kurdish situation as an oppressive occupation rather than a symmetric war; then fusion followed ideology there too. Fusion consistently predicted extreme, non-normative action, while ordinary activist identity predicted lawful protest. Among the aspiring YPG volunteers, the pattern reached its ceiling: they reported feeling more fused with Kurds than with their own ethnic group, and fusion predicted self-sacrifice and the reported likelihood of actually joining.

Why it matters

Solidarity and radicalization research usually stop at sympathy; these data trace the far end, where someone else's struggle becomes self-defining enough to die for. The mechanism is politically symmetric in principle — we note the untested mirror case of right-wing volunteers — and the caveats are real: extreme-action measures were short and skewed, only one study was experimental, and aspiring fighters' self-reports are not enlistment records. But the core claim held across every design: conviction plus perceived oppression can make strangers into kin.