"Blitzkrieg" on a strategic level means "attack the unprepared," while on a tactical level it means "strike the weary."
The idea is to never attack an enemy's prepared defenses, as that would only mire oneself in a terrifying quagmire.
A tank is not a gun turret; its greatest advantage is its mobility. It bypasses strongholds and fortifications, using thick armor, cannons, and machine guns against virtually defenseless infantry.
This is the so-called "pincer movement" of World War II.
At the same time, frontline commanders of the German Army have significant freedom. They can decide whether to fight or not based on the situation, or even choose their attack routes, as long as the general direction is correct.
As a result, many orders are made on the fly, creating a lack of patterns that leaves opponents confused.
At this moment, Shire is bypassing Mons, for which the German Army had painstakingly prepared, even at the cost of blood and lives.