How did an outnumbered, technologically outmatched, and overwhelminglyoutgunned Hamas preserve combat power for more than fifteenmonths while confronting a regional power that once routed state andnonstate forces in days? This study asks how Hamas fights and whetherits Hybrid Defence Strategy (HDS) has altered the balance of combatand military effectiveness. It dissects Hamas’s seven-pillar HDS—multi-domain operations, combined-arms synchrony, simultaneous shiftsin warfare modes, urban-subterranean weaponisation, light-infantry/IEDprimacy, horizontal escalation through allies, and an aggressiveinformation-ops campaign. Findings indicate that HDS confers tacticalagility and operational endurance: subterranean depth, pulse-wave fires,and micro-lethal ambushes slow Israeli tempo and inflate force-to-spaceratios, thereby downgrading defeat rather than delivering victory.Although the loss-exchange ratio still favors the IDF, Hamas transformsdecisive overmatch into a protracted, manpower-intensive siege, demonstratingthat an ostensibly outclassed “underground army” can imposestrategic drag on a superior adversary.