Tactician

Commanders, Pirates, Warlords. Each wants to wage war, but none can do so without a cunning tactician. For the first timer, it can take weeks or months of intense planning and strategy to formulate a viable strategy, but there are those who have honed their craft. In an instant they gauge a situation and know precisely how to achieve their ends. Even in the frantic moments between life-or-death attacks they maintain perfect control and awareness. 

While tacticians that fight in the front lines are certainly a force to be reckoned with, their true strength relies on their allies. Adventurers are fearsome in combat, but a with a tactician on their side their raw, often uncoordinated power can be focused into lethal fighting force. Removing key targets, cutting of retreats, harassing ranged attackers, not a mistake left unpunished, and no advantage left unused. In the end, if an enemy lives to think back on their fight against a tactician, it won't be a single devastating blow that led to their defeat, but instead a dozen of crucial attacks from a spread of sources all acting as the hands of one highly intelligent being.   

Orders

At third level you gain a resource called command points. You have a maximum command points equal to your half your fighter level (rounding up) plus your intelligence modifier (your total maximum command points can't be lower than one). You regain all spent command points on a long or short rest. You can spend your bonus action and some command points to carry out an order. Any ally must be able to hear you speak to be able to gain the benefits of an order. (for this class "an ally" also includes yourself)

Basic Tactics

At third level you gain access to two new orders:

Strike
Spend one command point to let an ally within 60ft spend their reaction to make one weapon attack on a target within the weapon's range. 

Re-position
Spend one command point to let an ally within 60ft spend their reaction to move their movement speed to a point of their choosing.

Defensive Tactics

At seventh level you gain access to two more orders:

Brace
Spend three command points to let an ally within 60ft spend their reaction to take the dodge action.

Retreat
Spend two command points to let an ally within 60ft spend their reaction to move their movement speed to a point of their choosing without provoking opportunity attacks.

Offensive Tactics

At tenth level you gain access to two more orders:

Focus Fire
Spend five command points to target an enemy within 30ft. All allies within 60ft of you add your intelligence modifier to their to-hit rolls against that target. This effect lasts until the start of your next turn. 

Advance
Spend two command points to let all allies within 60ft spend their reaction to move within 15ft of you. 

Bolstering Words

At fifteenth level your words inspire the will to continue fighting in your allies. When an ally is the only target of an order they gain temporary hit points equal to twice your intelligence modifier.

Advanced Tactics

At eighteenth level you gain access to two more orders:

Push Them Back
Spend two command points to let an ally within 60ft spend their reaction to make one weapon attack on a target within the weapon's range. In addition, if the target is large or smaller then they are pushed 5ft away from your ally.

Into the breach 
Spend eight command points to let an ally within 60ft spend their reaction to make one weapon attack on a target within the weapon's range. For this attack their defenses are compromised. If they are resistant to your damage they instead have no resistance. If they take the damage like normal then instead they are vulnerable.