Duelist. As a bonus action, the indefatigable can force one creature it can see within 30 feet of it to make a DC 18 Wisdom saving throw. On a failed save, the target has disadvantage on attack rolls made against creatures other than the indefatigable and can't willingly move further away from it. These effects end at the start of the indefatigable's next turn. Additionally, the indefatigable gains a +2 to damage rolls when it hits with its legendary longsword when wielded with one hand (included in the attack).

They Just Keep Going. Unlike magic users, fighters are just as effective at the end of the day as they are at the start. Rather than risk everything on a single battle, a squad is much more likely to chip away at an enemy's resources over a longer period of time, wearing them down until they are practically zombies. A worn out enemy is an enemy that the squad can beat with less risk, and being a fighter is all about managing risk.

Fighter Tactics

The Scourge of Spells. The biggest threat to a fighter is magic. Most haven't the faintest clue what it is, just from the fact that the vast majority of people living in the world don't interact with magic on a daily basis. Often, one member of a fighter squad will take the feat mage slayer expressly for the purpose of eliminating enemy mages as quickly as possible. Other effective tools against magic might include speed, sending a mounted cavalier or knight to close the distance on the wizard, or taking advantage of cover, tossing up smoke to undercut spells that require line of sight, or even some magical effects themselves if they have them available. An eldritch knight with a few scrolls of counterspell can completely neutralise an enemy spellcaster.

Hit and Run. The first round of combat is the most useful for a squad, especially if they have prepared an ambush spot ahead of time. Given time to prepare, even fighters wearing heavy armor can effectively hide themselves in an ambush spot. Once their ambush goes off, every fighter can burn their action surge to rain hell on their opponents faster than they can react. A battlemaster can spur an arcane archer to use multiple magical arrows on the same turn. A blood knight can release all of its pent up energy at once. A samurai can strike down its enemies with a single draw of its blade. And once the dust settles and the blood hits the dirt, the fighters can gallop away, leaving their opponents dazed, wounded, and demoralised, only for the fighters to strike again a few hours later.

Fighting Styles. A figher's fighting style plays a large role in how they are laid out tactically in a fight. Heavy weapons specialists and armored tanks rush forward, gaining extra attacks, inspiration, and heroic fortitude from support fighters like battlemasters and purple dragon knights. If many of the squad have shields, they will form up to defend each other (once spellcasters with area of effect spells have been dealt with). Archers, naturally, hang out in the back, dealing with stragglers and applying pressure. Different lines of battle naturally develop based on the individual strengths of each fighter within the squad. Throughout the fight, their constant barks of communication confuse the enemy while directing their teammates, and seeing a full squad acting in synchronisation is a sight to behold, at least until you're dead.