Last Z: Survival Shooter Unit Promotion Guide: How to Upgrade Troops

Promote lower-tier units directly to your highest unlocked tier at the Barracks instead of recruiting top-tier units from scratch. In Last Z: Survival Shooter, the promotion mechanic charges only the difference in time and resources between the existing soldier's tier and the target tier. This method preserves training speedups, maximizes competitive event points, and keeps your base defended without filling medical facilities with obsolete units.

How Unit Promotion Works

When you unlock a higher troop tier, standard recruitment for that tier requires full base resource costs and lengthy training timers. In contrast, selecting an existing unit batch and tapping Promote subtracts the lower unit's original investment from the new tier's requirements.

Action Type	Resource Cost	Timer Length	Event Point Value
Direct High-Tier Training	Full tier cost	Full base timer	Standard score per speedup minute
Unit Promotion (Low to High)	Cost difference between tiers	Time difference between tiers	High score per speedup minute
Passive Low-Tier Staging	Low tier cost	Short base timer	Low baseline score

Because you only pay the marginal difference, your Barracks queues finish substantially faster per soldier upgraded.

Staging Troops for Alliance Duel and Arms Race

Unit promotion provides the highest scoring density during troop training events, such as Day 5 of the weekly Alliance Duel and matching Arms Race cycles. Event points are awarded based on the final tier reached rather than the time spent training.

To maximize event rewards without exhausting speedups, use a two-phase staging strategy:

Stage troops on non-training days: Train intermediate units (such as Tier 7 or Tier 8) using standard passive timers while construction or research events are active. Do not use training speedups during this phase.
Promote during training events: When the training event opens, switch your Barracks interface to Promote. Upgrade your staged intermediate units to your maximum tier in bulk using training speedups.
Stack alliance buffs: Coordinate your promotions when alliance training speed buffs or titles are active to further reduce the remaining timer on each batch.

This cycle allows you to unlock daily event milestone chests with significantly fewer speedup items than direct high-tier training requires.

Base Defense and Hospital Capacity Management

Carrying large numbers of unpromoted, low-tier troops creates a defensive risk. During base attacks or territory battles, lower-tier soldiers take damage alongside elite units and quickly occupy hospital beds.

If your hospital fills to maximum capacity, excess casualties are lost permanently. Promoting outdated units ensures that:

Every defending soldier utilizes the higher base attack, defense, and health attributes of your top tier.
Hospital space is reserved for valuable high-tier assets rather than low-tier filler that consumes healing resources and recovery timers.
Drill Grounds capacity remains concentrated in full-strength combat marches.