The war in Ukraine has highlighted the fragility of European security and the urgency of developing credible deterrence mechanisms that go beyond financial or rhetorical commitments. According to recent debates, the most important element of any guarantee for Ukraine’s future stability must be a well-armed European deterrence force on the ground. This would not be a symbolic deployment but a concrete military presence stationed behind the front lines, ready to intervene rapidly. Its function would be twofold: to provide immediate operational support to Ukrainian units in case of renewed Russian offensives, and to send a clear strategic message to Moscow. Without such guarantees, every truce risks being temporary, as Russia would exploit the pause to rest, re-arm, and prepare for a new cycle of aggression. In this sense, deterrence becomes not an optional element of strategy, but the cornerstone of any long-term settlement.