The following homebrew adds a modern option to the Fighter class in 5E TTRPGs. All of the core Fighter class abilities can stay rules as written; see the official 5E System Reference Document (SRD v5) for details. Note: This subclass has not yet gone through playtesting.
Soldier
You are a trained combat professional, part of a disciplined force that wages war with precision and teamwork. Soldiers aren’t brawlers or lone heroes; they are strategists, marksmen, and leaders forged by experience and discipline. Whether you’re a modern infantryman, a power-armored commando, or an interplanetary trooper, your skill lies in using coordination, cover, and tactics to dominate the battlefield.
Level 3: Battlefield Discipline
You have learned to act decisively under fire, maintaining cohesion and composure.
Tactical Stance. As a Bonus Action, you can enter a focused stance that lasts until the start of your next turn. While in this stance, you gain one of the following benefits (your choice each time you enter it):
* Advance. Your movement doesn’t provoke opportunity attacks, and you gain +10 ft. movement speed.
* Suppress. When you make a weapon attack, you can impose disadvantage on the next attack roll made by the target before the start of your next turn.
* Covering Fire. When an ally you can see moves away from a creature you attacked this turn, that creature cannot make opportunity attacks against that ally.
You can use this feature a number of times equal to your Proficiency Bonus, regaining all uses when you finish a Long Rest.
Military Training. You gain proficiency in one of the following: Athletics, Intimidation, or Perception. You also gain proficiency with land vehicles and setting-appropriate ranged weapons (firearms or energy beam weapons).
Level 7: Fireteam Coordination
You fight best as part of a squad, anticipating your allies’ moves.
Combat Coordination. When you take the Attack Action, you can forgo one of your attacks to direct an ally who can see or hear you. That ally can use their Reaction to make one weapon attack or move up to half their speed without provoking opportunity attacks.
Bounding Advance. When you move at least 10 feet and then hit a creature with a weapon attack, an ally within 30 feet gains +2 AC against that creature’s next attack until the start of your next turn.
Level 10: Suppressive Fire
You can use your weapon to control space and movement. When you take the Attack Action, you can replace one of your attacks with a Suppressive Burst: Choose a 15-foot cone or a 30-foot line originating from you. Each creature in that area must succeed on a Wisdom saving throw (DC 8 + your proficiency bonus + your Dexterity or Strength modifier) or become Suppressed until the end of your next turn.
A Suppressed creature has disadvantage on attack rolls and cannot take reactions.
You can use this feature a number of times equal to your Proficiency Bonus, regaining all expended uses on a Long Rest.
Level 15: Tactical Reflexes
You react faster than most, trained to respond instantly to shifting conditions. You can take two Reactions per round, but only one per turn.
In addition, when you roll Initiative, you can immediately move up to half your Speed and draw a weapon as part of the same reaction, representing combat readiness.
Level 18: Combat Commander
Your presence on the battlefield elevates everyone around you.
Command Aura (30 feet). Allies of your choice within 30 feet who can see or hear you gain the following benefits while you’re conscious:
* +1 bonus to attack rolls.
* +2 bonus to saving throws against being Frightened.
* Whenever they hit with a weapon attack, they can move 10 feet without provoking opportunity attacks.
Inspire Grit. As a Bonus Action, you can call out to steady your allies. Choose up to three creatures within 30 feet that can hear you. Each gains temporary hit points equal to your Fighter level + your Charisma modifier.
Once you use this feature, you can’t use it again until you finish a Short or Long Rest.