A great deal of people are undoubtedly aware of the German Army's famous blitzkrieg campaigns to some extent. Bearing that in mind, let's take a look at how the concept of highly mobile warfare works out in COH. I'll be trivializing quite a lot of the real-life theory and practice behind the strategy, but so does the game. Anyone with any knowledge of game design will know the difficulties of implementing real tactical/strategic mechanics. For now I'll discuss the general usefulness of each non-doctrine specific unit and demonstrate the fluidity of Wehrmacht teching and how this influences a combined-arms strategy so important (in my philosophy) to good and flexible gameplay.
One very important aspect before considering the maneuvers one uses on the COH battlefield is the tools with which you execute your moves. Like chess, you can't normally expect to win against a fully stocked opponent with just a pawn and your king. Because you'll most likely be pwned hurhur nvm. I consider Wehr as a faction ideal for doing this because of their teching style and build options.
Tier 1: The Wehrmacht Quarters builds your Volks, MGs, Snipers and Motorbike. This allows you to counter either a US WSC or Barracks start; all you have to do is see which one he builds. Then there's the British, who starts with Tommies and maybe a Bren Carrier, no choice. As can be seen, there's fluidity in choice even at the first step. If he churns out MGs, use a sniper to pick them off. If he spams riflemen, use volks to skirmish them, with an MG behind to support; he can't do the same thing to you since his rifles and MGs are built from separate buildings. If he is an idiot and spams snipers, get a bike and squash them for massive exp. This ability to build everything from the same starting building is invaluable.
Tier 2: What we got earlier was the early game stuff; functional, adaptable, but it's not the best idea to go on using them again and again while your opponent techs higher. Luckily, Tier 2 still demonstrates the same adaptability, this time packaged with more resilience and firepower: Grenadiers; or Grens, Halftracks, AT guns and the Mortar. Grens are excellent infantry, and any player should get at least a squad or 2 of them to maintain infantry superiority. Decking them out with panzershrecks is a good idea to counter the US fast Greyhound strat. The AT gun normally isn't so important just yet, but it's useful to get one especially on wide-open maps, since it's long range can kill those light US vehicles fast. If he's going heavy on rifles, or you suspect ranger spam, bring out a mortar, very useful to have around since it doesn't really need micro, and kills quite a lot of enemy infantry without drawing as much attention as a rattling MG. For those who automatically think of AT-gun when faced with tanks, shreck Grens are a very good alternative, and very much more mobile. Halftracks are also a decent support option, since you can put rocket artillery or double infantry-killing flamers on them, which is cool.
Tier 3: Some choose to bypass this tier in favour of Tier 4. Nothing wrong with that (I stop at Tier 2 sometimes), but T3 does have plenty of nifty stuff, especially the appearance of your first armour. The Stug is your first "tank", a solidly armoured piece which can deal serious damage to any light vehicles and threaten careless allied tanks. Always a nice addition when well-supported by infantry like Grens. The Puma Armoured Car is an deadly infantry killer, and fast too. Nebelwerfers help a lot against entrenched positions and infantry concentrations; not bad at all for 4 popcap. The Officer is pretty low on my priority list, though some of his abilities are fun to play with like forcing his infantry to retreat, leaving his armour devoid of any infantry support, whereupon you can run in with shreck squads and tear his tank up.
Tier 4: Panzer Command. What we've been waiting for, the heavy armour. The tanks you can build here are top-of-the-line, unchallenged in their respective roles by any other faction's tanks (except perhaps the British Firefly, which is pure awesome on a stick). On the Ostwind and infantry, it just kills, kills, kills. The Panzer 4 is a decent MBT to have around, with good armour, anti-infantry and AT capabilities handled by the reliable main gun. The Panther is a serious threat to any allied tank force, with excellent frontal armour and anti-tank ability. But before it scourges your opponents' armour, it'll make a serious hole in your pocket, so get a good economy up. Knights Cross Holders, or KCH, are elite close-combat infantry which just don't die. On the expensive side and limited in tactical repetoire, a single squad is nice to have when you don't have a tank to soak up MG fire, but not a good choice to replace Grens with them.
Contrast this teching scheme to the more compartmentalized US way of teching, and we'll find that it leaves many options open to flexible play, especially in the critical early game. MGs and light infantry come out at the same time, allowing the MG-supported Lt Inf to overcome even heavy infantry like the British Tommies. The MG, played aggressively and shielded behind Lt Inf, is less vulnerable to snipers since the Lt Inf can charge down the sniper and kill it. Using this example, this is one way weaknesses of both the Volks (low health and firepower) and MGs (low mobility and vulnerability to snipers) can be greatly reduced by using them together, as well as bringing forth their strengths: Volks (maneuverable, fast), MG (high firepower and suppression, very impt when fighting tough Tommies). This is but one example we can use to showcase the idea of combined arms and unit synergy.