By focusing on keeping enemies off-balance, you help allies attack more effectively.

Whenever you hit a creature with a melee weapon attack, you can also take the Help action. On a critical hit, the target of your Help action can use their reaction to take the Dodge action.

You interpose yourself to take a hit for your ally.

When an ally within your reach is hit by an attack, you can use your reaction to swap places with them and become the target of that attack, taking half as much damage as normal.

Your strikes make foes hesitate, leaving openings for your allies to move free of danger.

You throw your ally at an opponent, lending them extra power.

As your ally strikes an opponent, you seize the moment of imbalance to knock them down.

You join in a

You and an ally tackle a foe together, your combined strength forcing them to the ground.

Choose an ally you can see. Your ally can use their reaction to move up to 20 feet to be adjacent to a creature you designate. 

You know how to fight while surrounded by foes and can quickly instruct an ally on how to move in concert to survive against an overwhelming number of foes.

Choose an ally within 5 feet. Until the start of your next turn, as long as that ally remains within 5 feet of you and is able to take actions, and both of you are unmounted, you and your ally increase your AC by 2. 

Watching a companion under attack infuriates you and you fling yourself at their opponent with a powerful shove.

After a creature within your reach makes a melee attack against an ally, you can use your reaction to make an Athletics check against the creature’s maneuver DC. On a success you shove the creature 10 feet away from you and you move 10 feet in that direction. 

Falling into step with a fellow warrior and putting both of your shields together makes each of you harder to hit.

While you are wielding a shield, you can choose one ally within 5 feet that is also wielding a shield. Until the start of your next turn, as long as that ally remains within 5 feet of you and is able to take actions both you and your ally increase your AC by 2.