Stamina
Stamina is a limited supply of energy displayed as a bar at the top left of the Player HUD.
Stamina Uses
Sprinting
Sprinting consumes stamina. The consumption rate increases the more encumbered the player is. Sprinting on a road rather than offroad reduces the stamina consumption rate ten fold, but it increases risk of getting run over. If overencumbered 
the player will collapse for a moment if their stamina bar goes under 20% and turns red.
Melee
Attacks with Fists, Bayonet, or Melee Weapons consume stamina. Parrying with a Melee Weapon continuously consumes stamina.
Swimming
Swimming in water consumes stamina except when the player is not moving. The player drowns if their stamina bar gets below ~12%. A full stamina bar always gives exactly 32s of swimming time even when overencumbered or sprinting. Players can "sprint" while swimming at no additional stamina cost. With full stamina a soldier can swim a distance of 55 meters if they sprint (47m without sprint) regardless of weight unless overencumbered which reduces the distance to 23m (20m without sprint).
Manning a crew seat that is underwater in the flooded compartment of a Large Ship also drains stamina. A full stamina bar is depleted in about 30 seconds then the player drowns.
Gas
Players inside a Green Ash cloud without a Gas Mask with a filter rapidly lose their stamina. A full stamina bar is consumed in just 4 seconds, after which the player starts taking damage.
Stamina Effects
The amount of remaining stamina impacts certain actions:
- The speed increase from sprinting compared to walking is proportional to the amount of stamina left. Sprinting with full stamina is 50% faster than walking but it is the same speed as walking with no stamina left.
- The time it take to shoulder a weapon by pressing
RMBdepends on the amount of stamina left. Shouldering is nearly instant at high stamina but can take up to a second at very low stamina.
Stamina Regeneration
Stamina only regenerates when the player is not sprinting or swimming. The more encumbered the player is the slower the regeneration is. Wearing a Gas Mask halves the regeneration rate. When stamina is used, it only starts regenerating after a 1 second delay.
In vehicles
While driving Vehicles, the stamina bar will be replaced by the Fuel bar showing the amount of Fuel remaining in the vehicle's tank.