Space Marine 2 Siege Mode Guide: Requisition, Wave Scaling & Boss Survival

Siege Mode in Warhammer 40,000: Space Marine 2 is a wave-based horde survival mode where three-player squads defend a fortress against endless Tyranid and Chaos enemies. This guide covers the requisition economy that keeps you alive between waves, the brutal damage and resistance scaling that starts at wave 11 and makes late runs unforgiving, and the concrete priorities you need to survive five waves, decide whether to evacuate or descend, and reach the bosses that cap the hardest runs.

Siege Mode is a wave-based horde survival mode added in the June 2026 update, where players aim to survive as many waves as possible, developed by Saber Interactive and published by Focus Entertainment. The battle unfolds within a fortified Imperial stronghold on Kadaku, relentlessly attacked by endless waves of Tyranid and Thousand Sons enemies; the fortress has three rotating sectors (Defensive Positions, the Arsenal, and the Control Room), and in each sector you face five waves before advancing to the next sector. Waves aren’t just killing enemies—your team will occasionally be asked to complete objectives, powering generators, investigating corpses, and similar tasks. It differs sharply from Operations mode because there is no linear mission structure and no endpoint except failure or voluntary extraction.

Your squad will be thrown into an enclosed area and must fight against waves of enemies, alternating between Tyranids and Chaos forces each sector. Brief one-minute intermissions between waves offer strategic opportunities, clearly indicated through UI notifications, and this is when you access Requisition Terminals to spend the currency you have earned. As you defeat enemies and complete objectives you’ll earn Requisition, a currency you can spend to acquire healing items, ammunition, grenades, and even AI reinforcements to assist you in battle.

Once your team completes five waves you’ll be taken to extraction, and you may choose to continue the Siege run or evacuate; leaving will grant all earned rewards, including Armory Data and Requisition Points. Choosing to descend means your squad pushes forward into a whole new sector—new arena, new scenery, new enemy faction breathing down your necks, and another five waves waiting for you. The choice is permanent for that extraction window: walk away with everything you have earned, or risk it to push higher for better loot.

Requisition is the in-run currency that determines survival. You can accelerate your Requisition earnings by completing objectives listed in the pause menu; there are challenges tied to your current run and your chosen class, and you should try to complete these as early in the run as possible to acquire buffs and reinforcements for the later rounds. Completing side objectives gives additional requisition points as a reward.

The Requisition Terminal sells supplies, upgrades, and reinforcements. Available purchases include Medicae Stimms, grenade bundles, five ammo crates, a reusable ammo cache, three armor boosters, and a self-revive relic. Recent updates added more items: Tarantula Sentry Gun, Tarantula Sentry Gun Upgrade, Tech-priest, Minefield, Disciplined Reinforcements, Techmarine, and Explosive Resupply. Reinforcements include Imperial Guardsmen, buffs for your squad, or a mighty Dreadnought to help turn the tide, though the mighty Dreadnought will be the most expensive of the bunch and will lay waste to enemies for 3 minutes.

Early-wave economy is the most common failure point. Many squads burn Requisition on immediate supplies or one-time reinforcements and then hit wave 11 starved for resources when scaling spikes. Persistent economy purchases—Tech-priest for resource generation, reusable ammo caches, sentry guns—pay dividends across multiple waves and let you stretch your budget when every Terminus enemy becomes a bullet sponge.

The scaling system is what separates casual clears from deep runs and why a squad that breezes through wave 8 can suddenly wipe at wave 13. Regardless of difficulty, every time the timer reaches zero and a wave is cleared after wave 11, enemies receive 4% less damage (up to a maximum of 60% for regular enemies and 80% for Terminus-level enemies) as well as deal 5% more damage (up to a maximum of 500%). That scaling is cumulative: by wave 15, regular enemies have 16% damage resistance and Terminus enemies have reached the cap or near it, while all enemies are dealing 20% more damage. By wave 20 you are fighting enemies with 36-80% damage resist dealing double or triple damage.

From wave 16 onwards, enemy melee attacks will start piercing armor and start damaging health if the damage exceeds the armor the player has, which removes the primary defensive buffer Space Marines rely on and turns every parry miss into a potential death. Recent updates adjusted the difficulty curve so enemies grow stronger much quicker and much earlier, with the intention to make Siege mode sessions quicker and more intense. This is why economy matters: a run that felt easy becomes a grind where you burn through ammo and healing twice as fast, and any lapse in Requisition spending leaves you unable to kill fast enough to survive the next spawn.

Patch 14 adds the Hive Tyrant and Mutalith Vortex Beast as wave-15 bosses (Patch 14 is on PTS, full release expected late July/early August 2026). These are the Operations-tier bosses, not smaller elites, and they inherit the full wave scaling bonuses. Because they land at wave 15, these bosses arrive with the full accumulated wave scaling stacked on their Operations-tier health pools — a regular-tier enemy sits at roughly 16% damage resistance by then, and Terminus-tier scaling climbs toward the 80% cap on deeper runs — so they deal massively increased damage and require near-perfect execution and likely a Dreadnought or full squad of Astartes reinforcements to bring down without casualties.

Boss waves are when you spend saved Requisition. If you have been building economy and saving big purchases, wave 15 is the time to drop a Dreadnought, buy every healing stim on the terminal, and coordinate abilities. The boss itself is a DPS check layered on top of the regular wave spawn, so you cannot ignore the adds and tunnel the boss or you will be overwhelmed; designate one player to kite adds while two focus the boss, rotate when armor breaks, and use parries to regain contested health and buy breathing room.

Siege rewards balanced squads more than Operations because there is no downtime and no chokepoint scripting you can rely on. Heavy is the anchor class: area-of-effect damage from the Heavy Bolter or Plasma Incinerator clears Minoris swarms and chips Majoris groups, and the class perks sustain ammo economy. Bulwark provides the defensive backbone with banner placement for contested-health regeneration and the Thunder Hammer for Terminus control. Tactical offers versatility with ammo boxes for the squad and Auspex Scanner to track priority targets during dense waves.

Assault and Vanguard are harder to justify in Siege because melee-focused classes struggle when enemy damage scaling makes every engagement a trade you cannot afford, and the lack of linear level design means fewer opportunities for safe flanking. Sniper can work if the player focuses on Majoris elimination and saves the cloak for clutch revives or boss DPS windows. The most reliable squad is Heavy, Bulwark, Tactical—maximum sustain, maximum crowd control, and enough flexibility to adapt when the wrong Atonement rolls or a bad spawn wipes your positioning.

The evacuation decision at waves 5, 10, and 15 is a risk-reward calculation based on three factors: your squad’s current Requisition and health state, the Atonements rolled for the next sector, and whether you have the class composition and coordination to handle the next tier of scaling. If you finished wave 5 with less than 300 Requisition banked, you are already behind the economy curve and descending will likely end in a wipe by wave 8. If a teammate is learning the mode or running an underleveled class, extracting at wave 10 with a solid reward haul is smarter than gambling on wave 15.

Descending makes sense when your economy is healthy (Tech-priest placed, ammo cache bought, 400+ Requisition in reserve), your squad has cleared the sector without using all healing or reinforcement purchases, and you want the exclusive cosmetics and Armory Data that only drop from higher waves. The difficulty spike between sectors is not linear—wave 11 is harder than wave 10 by a larger margin than wave 6 is harder than wave 5, because scaling starts at wave 11 and Atonements can stack negative modifiers that make certain builds unviable. If you roll an Atonement that nerfs your primary damage source and cannot afford the 250-Requisition reroll, evacuate.

Armory Data and Requisition Points

You earn points with each wave you defeat and spend them at Requisition Terminals to stay in the fight; extract before it is too late to earn Requisition Points, Armoury Data and XP. Requisition Points are rewarded through playing PvE or PvP and are used to unlock new versions of weapons, class perks, or Heraldry armour customization; the amount you can store is limited to a maximum of 2000 Requisition Points. Armory Data unlocks cosmetics and weapon variants in the progression system, and the amount you earn scales with how many waves you clear before extraction.

Exclusive Cosmetics and XP

Siege mode itself, alongside its exclusive cosmetic rewards, are free, meaning you do not need to purchase DLC to access the mode or earn the unique armor pieces and heraldry tied to wave milestones. Class XP gain in Siege is comparable to Operations but concentrated in shorter sessions, making it a viable alternative for leveling if you can consistently reach wave 10 or higher. The real chase rewards are the cosmetics locked behind wave 15 and 20 clears, which require mastery of the economy and scaling systems.

Blessings System

Recent updates added Blessings and Atonements system: every 5 waves, receive a permanent blessing in the new Shrine and endure shifting atonements. Blessings are permanent positive modifiers for the run (increased damage, faster ability cooldowns, bonus armor), while Atonements are negative modifiers that last one sector. Atonements last for one sector and they are replaced every time players reach a new sector; players can reroll the atonements by spending 250 Requisition. The Blessings system adds a rogue-lite layer that rewards deep runs with compounding power, but bad Atonement RNG can brick a run if you cannot afford rerolls.

Myth: Reinforcements Are Always Worth Buying

Cadian Guardsmen and Astartes reinforcements look powerful but are expensive and die quickly once scaling kicks in after wave 11. Many squads waste 500+ Requisition on a Dreadnought at wave 6 when that currency would have bought a Tech-priest, ammo cache, and sentry gun that sustain you through wave 15. Reinforcements are situational tools for emergencies or boss kills, not baseline purchases.

Myth: You Can Ignore Objectives and Just Kill

Side objectives are the primary source of bonus Requisition and skipping them to farm kills leaves you starved for economy in later waves. Objectives also break up the spawn rhythm and give you windows to reposition or heal without constant pressure. A squad that clears objectives efficiently will have 30-40% more Requisition by wave 10 than a squad that ignores them, and that gap is the difference between surviving wave 15 and wiping at wave 13.

Myth: Scaling Is Linear and Predictable

Wave 11 is the cliff. Squads expect difficulty to ramp gradually and instead hit a wall where suddenly every Terminus enemy is a raid boss and Minoris swarms that were trivial now chunk armor in seconds. The 4% per-wave resist and 5% per-wave damage increase do not feel dramatic in isolation but compound exponentially, and by wave 15 you are fighting a completely different game than wave 10. Plan your economy and extraction around wave 11 as the hard breakpoint.