The major striking force of your troops and best units to lead an attack are tanks. Tanks are the basic tool for breaking the enemy's defense lines. They have an armor that is immune to infantry weapons and can destroy most of the enemy targets. Their biggest enemy are the anti-tank guns, hidden somewhere in the forest, and the enemy planes, against which the tanks are defenseless. Panzer units can occupy the area and take over strategic points. Therefore, it is sometimes worthwhile to occupy a poorly defended territory and bring in reinforcements to secure the area. Tanks have a huge range of guns, from 1 to 2 kilometers. If you place such a unit on a hill with a view of an open area, you can turn such zone into a deadly field. Don't forget the anti-aircraft units, as static tanks are an easy target for enemy bombers.
Tanks don't have their own "health bar" like soldiers, but can be damaged by destroying their movement mechanism, towers or engines. A highly damaged tank, can be abandoned by the crew and even surrender. You can repair such units with the help of supply trucks. Just park it close enough to the unit and it will restore the tank to its full combat power. Of course, some hits can be critical, e.g. an explosion of ammunition or a killed crew, which results in immediate destruction of the unit.
The German side will often have available some conquered French tanks (Panzer 39H(f)), Russian tanks (Panzer T-70, T-34) or even Polish tanks (Panzer 7TP(p)). In turn the Russian side, will have a large range of American and British tanks on the basis of Land-Lease agreement, or M5, Sherman and Valentine tanks.
Remember, almost all tanks have poor optics and the ability to hide from the enemy. Always use other units, such as scouts, infantry or airplanes, to help them track down your opponents and not let them destroy you too easily.
These armored vehicles are small, fast and cheap units, but with low firepower and poor armor. They are suitable for attacking weaker resistance points, as infantry support or for raids attacking the enemy from the back. They are also ideal for attacking flanks or cutting off enemies from the main front. In large groups they can be deadly, even for heavily armored vehicles. It is enough for some vehicles to divert the enemy's attention, while other vehicles will circle the enemy and attack the weak back of the tank.
Tanks can confront almost any troop. Their strong armor makes many missiles simply bounce back from them. In a group, they can annihilate almost any enemy, even anti-tank cannons. It is worth taking infantry or reconnaissance with them to quickly destroy enemies.
These are your army's lead units - reasonable value, strong armor, and versatile cannons that can handle almost any opponent. With these units, you will lead most of the attack. They will withstand a massive fire of the enemy, and in a large group can be very dangerous, even unstoppable. Remember that they still have weak armor on the sides and rear, although their front can be very strong. It is worth to position such units, that e.g. buildings or forests can protect their sides from an enemy's armored counterattack. In this way, the tanks will always be facing the enemy.
Powerful steel beasts with the strongest armor of all units. Also, they have powerful cannons that can penetrate practically any enemy armor. Such vehicles have front armor almost twice as strong as most tanks available in that period, and their side armor is often equal to the front armor of medium sized tanks. At the same time they are very expensive and slow units, which makes them an easy target for enemy air forces. What is more, their availability in divisions is very modest, and the valuable points of acquisition is quite high. That's why the loss of any such unit can be very painful. Don't let them go in the first line of attack, as you may lose them too quickly. Single and lonely heavy tanks are also an easy sacrifice for your infantry and anti-tank units.
They operate on the same principle as infantry leaders. They spread the aura of command and leadership to nearby units (all of them, not only tanks), so that everyone in their range have a +1 to experience bonus. Their price is similar to that of regular troops, but they are more effective than infantry leaders (armor, cannon). For obvious reasons, these units have problems to hide, so the enemy can easily track down such tanks. Leaders should be the main target the opponent's groups, because of the strengthening of the other units. Moreover, many of these units have a radio and can help the artillery to carry out accurate fire in their vicinity.