Gimbutas believed that the expansions of the Kurgan culture were a series of essentially hostile, military invasions where a new warrior culture imposed itself on the peaceful, matriarchal cultures of "Old Europe", replacing it with a patriarchalwarrior society, a process visible in the appearance of fortified settlements and hillforts and the graves of warrior-chieftains:
- The Process of Indo-Europeanization was a cultural, not a physical transformation. It must be understood as a military victory in terms of imposing a new administrative system, language and religion upon the indigenous groups.
In her later life, Gimbutas increasingly emphasized the violent nature of this transition from the Mediterranean cult of the Mother Goddess to a patriarchal society and the worship of the warlike Thunderer (Zeus, Dyaus), to a point of essentially formulating feminist archaeology. Many scholars who accept the general scenario of Indo-European migrations proposed, maintain that the transition was likely much more gradual and peaceful than suggested by Gimbutas. The migrations were certainly not a sudden, concerted military operation, but the expansion of disconnected tribes and cultures, spanning many generations. To what degree the indigenous cultures were peacefully amalgamated or violently displaced remains a matter of controversy among supporters of the Kurgan hypothesis.