A static defence is one where the tanks deploy within the first minute of play and remain generally in that position for most of the game until their death. Defence should not be static structure. WOT is a game that encourages manuevre and mobility of its tanks. You can recognise a static defence by the following features:

a. Tanks do not change Fronts.
b. Tanks occupy a DZ from the beginning of the game until their deaths.
c. Tanks in line defence, when facing a flank enemy attack do not readjust their positions.

Dynamic Defence is a crucial doctrinal concept to understand. It evolves from the basic theory that we need to respond to enemy positioning and actions. We cannot execute our own plan oblivious to enemy action.

Dynamic Defence is the
conscious defensive redeployment of own forces in response to enemy actions. There are three common scenarios (using RBAT mode as an example) that can be used to better understand this concept.

Scenario 1 - Changing Fronts: The lone scouting tank on a DF (Defensive Front) encounters an overwhelming enemy force which is quickly assessed as the bulk of the enemy’s tanks. The common error is for both the own force 1F an 2F to press on to the enemy base, engage the enemy defence and hope to win the capture race. This decision actually allows the enemy’s “all-in” gambit a chance of success. The application of Dynamic Defense principles here would ask one of the Fronts to turn back to engage and HOLD the main enemy force while the other Front continues to press towards the enemy base. Whether 1F or 2F turns back cannot be governed by doctrine. It has to depend on the quality of tanks on each Front and their distances from their own base and the enemy base. In the illustration below, tanks from 1F redeploy to reinforce and HOLD the enemy at DF.
Scenario 2 - Turning the defence line: This scenario occurs on several maps, but is most stark on maps such as El Halluf and Steppes. It occurs when the defence is initially positioned as a forward facing line, to defend the middle or to snipe at the enemy. As the battle evolves and the enemy attack down the flanks, the enemy eventually reaches one of the edges of the defence line. The common error here is to remain static and just turn the tank to face the enemy. More often then not, the far side of the line cannot engage the enemy yet. What happens is that the enemy tanks will destroy the line tank by tank, like Pacman eating a line of dots! This happens because the mass of enemy tanks can concentrate their fire on the one or two defending tanks that can actually engage them, whilst the rest of the defenders are “waiting” for the enemy to come into their engagement envelope.

Dynamic Defence principles would ask the defenders to
turn the whole line to move and engage the enemy. The reason to do this is to meet the enemy force with the maximum amount of concentrated fire and prevent the enemy from only engaging one tank at a time. At TACT, we recommend turning the line using a method called “Compression” which is illustrated below.
In the illustration above, it has been suggested that tank 1 does not move and "sacrifices" himself to allow time for the remaining forces to compress. In practice, unless the defensive line is late in reacting, this is not necessary and only serves to waste tank 1.

Scenario 3 - Loss of all base defence: This occurs when our last tank defending the base is destroyed. Often, teams will continue to press all their tanks towards the enemy base in the hope to win the capture race. This works some of the time. However, by redeploying 1-2 fast tanks back to own base to hamper/ reset the enemy capture, the chances of victory are considerably improved. In a real example of Dynamic Defence:

“The map was Malinovka. We had 3 tanks left and the enemy only 2, but they had commenced capture sometime before us. There were no other tanks or arty left. A loss would have been imminent. However, our team had sent a KV-13 back to own base the second the enemy cap started. He arrived and managed to place a HE round on both tanks before being destroyed. By resetting the enemy capture, we won the cap race.”

TACT Tip: When attempting to reset capture, using HE instead of AP increases the chances of doing that single point of damage required to reset the cap for that tank.