Fallout Shelter: How to Defend Against All 4 Vault Attackers

To defend against external attackers in Fallout Shelter, build a defensive gauntlet across your vault's top floor. Station armed defenders at the Vault Door and pack the first adjacent room—ideally a three-wide production room staffed by six dwellers—with your highest-damage weapons. When an alarm sounds, identify the invading faction while they breach the door, prepare medical items, and manually heal defenders before the threat spreads deeper into your base.

External Attacker Threat Profiles

External incidents originate outside the vault and force invaders to batter through the Vault Door. Each enemy type threatens different resources and requires specific defensive reactions.

Attacker	Damage Profile	Primary Threat	Key Response
Raiders	Low-to-moderate physical	Drains Caps, Food, and Water	Upgraded Vault Door, mid-tier rifles
Feral Ghouls	Physical with heavy radiation	Shrinks maximum dweller HP	RadAway reserve, rapid post-fight triage
Aliens	High burst energy damage	Rapid single-target health drops	Manual Stimpak healing below 50% health
Deathclaws	Extreme physical damage	Massive Food drain and room clearing	High-DPS weapons, high-Endurance dwellers

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Repelling Raiders

Raiders focus on resource theft, siphoning Caps, Food, and Water for every second they stay alive inside your vault.

Delay the breach: Upgrading your Vault Door increases its durability, giving you extra seconds to position armed defenders or drag backup into the entrance.
Clear them in the first room: Two guards at the door rarely eliminate an entire raiding party. Let the surviving Raiders filter into your first adjacent three-wide room, where six workers armed with hunting rifles or combat shotguns can finish them before they reach lower floors.

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Countering Feral Ghouls

Feral Ghouls inflict radiation damage that turns dweller health bars red. Because radiation caps maximum health, standard Stimpaks become ineffective until the radiation is removed.

Stockpile RadAway: Keep a reserve of at least 15 to 25 RadAway packs once ghoul encounters begin appearing.
Cure radiation before healing: Apply RadAway first to remove the red bar, then administer Stimpaks to restore lost health.
Perform post-combat triage: Immediately inspect every dweller in the affected rooms once combat ends. Irradiated survivors will die quickly in subsequent incidents if their maximum health remains reduced.

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Surviving Alien Invasions

Alien squads wield energy weapons that inflict concentrated single-target burst damage. Unlike Raiders, Aliens can melt a dweller's health bar in seconds.

Heal manually and proactively: Watch individual health bars throughout the fight. Do not wait for low-health alerts; tap directly on targeted defenders to administer Stimpaks the moment their health drops below 50 percent.
Equip sturdy defenders: Place dwellers wearing high-Endurance outfits and wielding strong energy weapons or shotguns in the top rooms to absorb burst fire without collapsing.

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Stopping Deathclaw Incursions

Deathclaws represent the deadliest external threat. They deal massive physical damage, rapidly deplete Food reserves, and do not remain in one chamber until killed. Instead, they attack for several seconds before sprinting into adjacent rooms in a continuous patrol loop.

Stack maximum raw damage: Equip your top floor exclusively with your highest-DPS weapons, such as Plasma Rifles, Flamers, and Missile Launchers. Raw damage output is the only metric that cuts down the Deathclaws' movement cycle.
Use high-Endurance dwellers: Dwellers leveled with high Endurance possess larger health pools, allowing them to withstand consecutive Deathclaw strikes without dying instantly.
Pre-heal between room transitions: The moment Deathclaws sprint out of a room into the next chamber, immediately use Stimpaks on the wounded dwellers left behind. This ensures they are at full health if the Deathclaws survive and cycle back.