Revisiting Combat as Sport vs Combat as War

[Yora]

Presence or absence of tactics is completely irrelevant to the distinction.

It's really all about the mindset with which you go into a fight, and the expectations of how battle is conducted.

Games with the d20 systems are usually considered the most prominent examples of Combat as Sport: Both sides meet on a level playing field, both with a limited set of approved and "legal" moves, with the expectation that they have a contest to determine which side makes the better thought out use with the moves that are available to them.
Players go into a combat encounter anticipating to be challenged by the GM, and looking forward to test and show how well they understand the abilities on their character sheet and the rules of combat in the rulebook. Combat as Sport is a logic puzzle that can be solved analytically. Using methods that are considered to be "cheesy" is frowned upon as it goes against the spirit of the game.

Combat as War is a very different approach. In Combat as War, there is no expectation that a combat is fair. The odds are stacked against the characters and the GM is expected to pull all kinds of nasty tricks. The challenge for the players is not to find an optimal solution to how the basic combat moves and the special abilities of their characters can lead to victory in an even fight, where the enemy is fighting the same way.
Fairnes and using the rules as they are intended is not the expectation in a figt that is Combat as War. The only goal is to win, by whatever means necessary. Using cheesy exploits in the rules is not considered bad sportsmanship, it's regarded as the right way to play. The way that the game is supposed to be.

In Combat as Sport, the players and GM have a gentlemen's agreement and mutual understanding that the enemies the characters face will not be too difficult to defeat, and that the players play the game according to the spirit of the rules.
In Combat as War, both the players and GM try to constantly outsmart each other by coming up with unusual and unexpected setups and outlandish improvisation.

Combat as War can be very tactical, but generally we find this approach to combat in games with very general and vague rules. Improvisation and thinking outside the box are the name of the game. You never really know what to expect and players are supposed to think on their feet when they are thrown into situations they've never had to deal with before.
Combat as Sport is more common in games with very elaborate and specific rules that aim to cover as many probably cases as possible. In these games, players have extensive to full knowledge of all the factors that can come up in a fight.

Sport has rules, and when people don't stick to them there is little point to even play.
In war, everything is permitted if it helps you win.

In my experience, Combat as Sport requires much more attention to the details of an encounter and careful deliberation of every move. Combat as war tends to be more of a fun romp where you go wild. Because when the rules are flexible, players don't have certainty of what a die roll will mean exactly. Things rely much more on the GMs judgement if an action sounds clever and sensible and whether it should work out because it was a great idea, or make little difference because it was pretty dumb.