For example, in the context of the Normandy invasions, is it fair to say that the strategy of Eisenhower et al. was to start a western front, to further split and strain Axis forces, and bring about a quicker end to the war, whereas their tactics were to invade the beaches at Normandy and secure a deep water port and a foothold in France? Further down the line, would the strategy of the 101st Airborne be to secure a foothold in France, while the tactics may be to secure a bridge to prevent an attack on the Allied flank?
You seem like youve got the basic idea ready, but maybe have confused a bit of the detail. Also, youre talking about World War Two, but are leaving out a key (but oft forgotten) middle step, and thats the Operational Art, or the Operational phase (operation planning, take your pick. Operations).
So, lets first get this out of the way. Below here, Im going to talk about the strategic art of war. Especially if you play video games, the word "strategy" has taken on a loose meaning, sort of like "any sort of martial plan, or long term plan". E.g. Starcraft, is a real time strategy game. Its not, in the technical definition of the word. Below here, I will talk about technical strategy. It may be hard to keep straight, but that distinction is fundamental to any talk of the three levels of military planning.
So, what are the three levels? Well, at the top you have "Strategy" or "Strategic planning". The US Department of Defense publishes a dictionary defining basic military terms. Therein it defines the Strategic Level of War as:
The level of war at which a nation, often as a member of a group of nations, determines national or multinational (alliance or coalition) security objectives and guidance, and develops and uses national resources to accomplish these objectives. Activities at this level establish national and multinational military objectives; sequence initiatives; define limits and assess risks for the use of military and other instruments of national power, develop global plans or theater war plans to achieve these objectives, and provides military forces and other capabilities in accordance with strategic plans. (emphasis added)
Now, I have a few problems with this definition (who says only coalitions can have strategy? Is there a difference between national strategy and high level military strategy? Should the military concern itself with setting national strategy?), but lets run with it. Importantly, it sets out two concepts. The first is that strategists need to set large objectives, which span across nations, regions, and the globe. Then, they have to allocate the forces necessary to accomplish those objectives. Now, these questions are actually a lot more political than you might think, and politicians should have of input on military strategy, as it affects the nations political strategy (lets ignore this, potential fourth level of strategy). Strategy is also a long term deal. Its shouldnt (in a perfect world), consider just the immediate future, but the course of the entire war. It deals in the beginning, the middle, and the end of hostilities. Strategic planning controls everything from when the mobilization of forces should begin, to what victory will look like, when its finally achieved.
Think of Desert Storm for this. The US formed a coalition with the goal of liberating Kuwait. It had a well defined political outcome, and set a military objective based on that goal. It committed military forces, which it felt was appropriate, selecting from a "tool kit" of options which ranged from small-scale special forces attacks through to nuclear annihilation. Once this strategy was set, commanders in the field were tasked with accomplishing these objectives.
And, very simply, tactics is the act of actually accomplishing those objectives. Our dictionary says:
The level of war at which battles and engagements are planned and executed to accomplish military objectives assigned to tactical units or task forces. Activities at this level focus on the ordered arrangement and maneuver of combat elements in relation to each other and to the enemy to achieve combat objectives. (EM)
Here, we have combat in its realist form. Tactical activity spans the gamut from the individual soldier, to the platoon, company, the brigade, or even the division. It deals with actual battle, and the manner in which military forces actually win (or lose) those engagements. Tactics are immediate, measured in weeks, days, hours, and minutes. Its the difference between life and death, the nitty and the gritty. Its every war movie youve ever loved, and the meat of the most popular strategy games. So, simple, right?
But we seem to be missing key component, here. If youve kept with me so far, youll have noticed that weve set political objectives, and military objectives. Well, for most of human history, tactics and strategy operated in harmonious conjunction. Often, national strategy was held by one man, or one small group of men. This was the King, Emperor, Monarch, or Parliament. The monarch would usually, either in person or vicariously (usually through a family member, influential noble, or prominent general) set strategic goals (usually, it was the destruction or capitulation of the enemy. Sometimes, though, that was not possible). They would then command their unitary army to accomplish this goal. At some point, they would stumble across the enemy army. At that point, strategy flew away, and the tactical phase ruled. What mattered was defeating the enemy, destroying their army, or at least not being destroyed yourself. (All of military history condensed into three rough sentences. PhD plox.)
Lets take a historical example, the Gettysburg Campaign. Roughly, Confederate National Strategy was simple, dont lose. Robert E. Lee, who was the arbiter of Confederate strategy in the East worked with the Confederate leadership to develop the framework of his offensive strategy. He hoped to take the war to the largely unmolested North, to destroy the PA Rail Road, to win a decisive victory, and maybe fiddle with Washington. Lee led the Army of Northern Virginia north into Pennsylvania, in an attempt to accomplish said strategy. But, as we all know, he was met in Gettysburg by the Army of the Potomac. At that point, all that strategy went away, and commanders in the field began to devise the best way to defeat the enemy, given the constraints of the army, and the terrain of the battlespace. No more thought was given to Washington, Richmond, or any other strategic objective until after the issue at Gettysburg had been decided.
Thus has war been fought, for thousands of years. But, youll say, you talked about a third level of war! An in between, called the Operational level of war. This is a funny thing. Operational warfare is a relatively new concept in warfare, and thus has no hard definition. The dictionary says, on the issue:
The level of war at which campaigns and major operations are planned, conducted, and sustained to accomplish strategic objectives within theaters or other operational areas. Activities at this level link tactics and strategy by establishing operational objectives needed to accomplish the strategic operations, sequencing events to achieve the operational objectives, initiating actions, and applying resources to bring about and sustain these event. These activities imply a broader dimension of time or space than do tactics; they ensure the logistic and administrative support of tactical forces, and provide the means by which tactical successes are exploited to achieve strategic objectives. (EM)
This is, actually, a fairly good definition of the operational art (operational lvl of war). Essentially, its a step in between strategy and tactics, which seeks to link tactical reality with strategic hopes. It last days, weeks, and months, and is only concerned with bringing strategic objectives to fruition. But its still a wriggly thing, hard to pin down and define.
The general maxim Ive always learned is thus: Platoons, Brigades, and Divisions practice tactics; nations practice strategy. So who then practices operations? Heres the sticker, and makes a practical definition hard. Our definition deals a lot with the coordination of military forces to achieve objectives. Following strictly this definition, Corps (tens of thousands of men, in their modern form), Armies (tens-hundreds of thousands), and Army-Groups (hundreds of thousands to millions) all practice the operational art. But others will say "no, only Armies do it". This is annoying, because it makes it hard to date the emergence of the operational art. If you say Corps, then this level emerged as early as the campaigns of Napoleon. If you say armies, then you suggest a start as late as World War Two.
Confused yet? Dont worry about it. For all practical purposes, just remember our basic definitions: Strategy is long term, long scale political objectives; tactics is small scale objectives and immediate combat; operations links the two. (If youre still iffy on the operational art, let me know and Ill hit you with an example, otherwise this post is tooo long as it is).
You got the right idea but you're missing on your scale for one, and two, you missed a third category that has come into the frontline of military thinking around the 19th century and came into practice in the 20th with the coming of much larger armies -- operational. Let's start from the top down with something that we are all most familiar with in my area of study -- World War I -- from the perspective of the Germans.
There are four "levels" of war that I will define for you as best I can and how I understand it:
STRATEGY --> OPERATIONS --> campaigns --> TACTICS*
From the top, the Strategic Level of Warfare is the overall plan for a conflict. In our situation, the strategy of the German Empire in 1914 was the rapid deployment of troops to the West to cause the rapid capitulation of France and then to swing East and take out the Russians as they finish mobilizing. It also has to deal with how this will be done by exploiting the nations resources and power. What railroads will be used for mobilization? What will the rations be for the civilian population? How many rounds a day will be producing? etc. This is where terms like total warfare fall under, basically.
Operational Level Warfare is how the strategy will be carried out. More specifically it is concerned with the planning a series of Campaigns which carry out the general operational plan. These are the "lines on the map" you can say and for us is where the Schlieffen Plan and later the Schliefen-Moltke Plan fall under. Kluck's 1st and Bulow's 2nd Army's would be the 'hammer' which would swing through the Belgian countryside and strike the decisive blow while Hausen's 3rd Army would provide them support as the "hinge" between the hammer and the holding "anvil" force. More familiar plans like Operation Barbarossa and Operation Overlord fall under this category.
Campaigns are a pretty nuanced subject, hence me lower casing it and giving it an asterisk. It's not technically part of the "three levels of war" defined by Clausewitz and other military thinkers. It's the inbetween love child between tactical level warfare and operational level -- it's the individual campaigns of the Generals carrying out the overall operational strategy. So Bulow and Kluck and Rupprecht and Hausen's each individually had campaigns under the Schlieffen Plan.
Next we have tactics which are as you describe -- company's and platoons and squads taking individual objectives for the purpose of performing a campaign.
So let's run through it with a scenario:
The strategy of Germany was the rapid deployment of troops West to cause the immediate capitulation of France. The Operation was the Schlieffen Plan -- holding force on the Franco-German border while 3 armies swing through Belgium and act as a decisive blow against the French. Hausen individually would perform a campaign where he would swoop down parallel to the Meuse River through the Ardennes and seize Namur to allow a Southern passing point across said Meuse. The tactics would be individual Company's assaulting said town by, for instance, taking a series of hills to gain an advantage against the defenders and use artillery to batter them out of the forts.
If you want a more in depth study of this I'd really recommend the go to book for any military historian -- On War by Carl von Clausewitz.
You've got it. Strategy is the "What" (more broad), tactics is the "how and who". Things on the battlefield don't strictly fit into one category or the other, however.