Strategy - A prudent idea or set of ideas for employing the instruments of national power in a synchronized and integrated fashion to achieve theater, national, and/or multinational objectives.
Strategic level of warfare — The level of warfare at which a nation, often as a member of a group of nations, determines national or multinational (alliance or coalition) strategic security objectives and guidance, then develops and uses national resources to achieve those objectives.
Tactics - The employment and ordered arrangement of forces in relation to each other.
Tactical level of warfare — The level of warfare at which battles and engagements are planned and executed to achieve military objectives assigned to tactical units or task forces.
Operation — 1. A sequence of tactical actions with a common purpose or unifying theme. (JP 1) 2. A military action or the carrying out of a strategic, operational, tactical, service, training, or administrative military mission. (JP 3-0).
Operational level of warfare — The level of warfare at which campaigns and major operations are planned, conducted, and sustained to achieve strategic objectives within theaters or other operational areas.
To put this within the context of an easily referencable D&D "game", I'll talk about the Order of the Stick webcomic.
Roy, the main character, has two strategies. The first is to take down Xykon. The second, later acquired, is to stop the current machinations surrounding the Gates, which contain a god-slaying abomination before the Gods solve the problem themselves, by destroying the planet entirely.
Roy's first Operation, in comic, towards those ends, was when he gathered the Order of the Stick and assaulted Durakan's Tower to fight Xykon head-on.
Later, during a completely different Operation, Roy is dueling Xykon, when Xykon, as a tactic to resolve the duel, offers Roy a new Strategic concern: That Roy needs to first attain additional levels before actually having a legitimate fight with Xykon. The prudence of this strategic advice is proven when the Operation ends(for Roy) with his death.
And while Roy's team often disagree on choice of Operations(Celia and Haley about what towns to search, with Haley failing to share Operational Intelligence she has), or more notably, Tactics(Belkar kills more people than Roy would allow), not even Belkar defies Roy's overarching Strategic goals. This is notable because in a 0-pvp ttrpg, that's what you want. Players, and characters who all agree on or concede to the Team's over-arching Strategic goals. With the OotS comic, that's the same thing, practically as Roy's Strategic goals.