During World War II, the anti-tank guns were developed at a much faster pace than the tanks. Therefore, the armour sufficient one day, could be obsolete the next. Naturally, discarding the vehicle was unrealistic, and therefore, field conversions were made to enhance the armour protection. The Germans used such additional protection especially in the last years of the war, where it was too expensive and often impossible to upgrade equipment.
The need for thick additional armour was usually dealt with my bolting on armour plates to the existing ones. This was also done by the Russians, although these rather welded than bolted the armour plates on. The Germans did initially weld on the additional armour, but switched to bolts, because it was easier. In 1941-01, a general ban for the field work shops to weld on armour was issued, because there was a fear that poor weld seams would weaken the armour, rather than stregthening it. This was a fast way to deal with new and more powerfull anti-tank guns, and was used on the Ferdinand, the Pz.Kpfw.IV and the Sturmgeschütz III, to name some. The bolted-on plates were usually only used on the frontal armour, thus adding additional weight to the front roadwheels.
After encountering Russian anti-tank rifles, namely the 14.5 mm. PTRD and PTRS, which were small, easy to conceal and very effective against especially the side and rear armour of German tanks - up to and including the Panther - thin metal sheets were hung on rails along the sides of the tanks. These were usually 8 mm. thick, and were made in sections, which could easily be replaced if damaged or lost. They were hung onto the rail on a series of spikes by loops welded on the back of the sheets.
It is often believed that Schürzen were used as a protection against hollow-charge ammunition, however this is not the case. For a more in-depth explanation of this myth, read about the true purpose of Schürzen.
Schürzen were used on the Pz.Kpfw.IV, Sturmgeschütz III and Sturmgeschütz IV and the Panther. On the Pz.Kpfw.IV Ausf.J, the thin metal sheets were replaced by a wire mesh (Thoma Schürzen). This type of Schürzen had been a competitive design to the solid plates, but the plates were initially chosen because production was easier with the existing machinery.
Similar in appearence to Schürzen was spaced armour, but it had a completely different purpose. The spaced armour was mainly mounted on the Pz.Kpfw.III, with a few Pz.Kpfw.IVs receiving it as well. It was installed as a defence against APC ammunition, where the spaced armour would strip the cap from the grenade.
Especially the Pz.Kpfw.IV and Sturmgeschüze used track links as additional protection. Originally, the tanks own spare tracks were carried on the frontal armour. They proved to add some protection, and in late-war pictures it is the rule more than the exception to see Pz.Kpfw.IVs with spare tracks everywhere. Not only the vehicles on tracks were used - T-34 track links have been seen covering vehicles almost completely. There are also been pictures of Panthers and Bergepanthers using track links in as protection.
On Sturmgeschütze, concrete were sometimes used to reinforce the weak roof of the vehicles. The concrete was simply poured onto the roof, filling holes in the roof. On the Sturmgeschütz IV, there were also large blocks of concrete placed on the front of the vehicle.
Sandbags were not used as much by the Germans as the western Allies, but they were still used. The sandbag provided some protection against greandes, that would have to push through the bags first.
All contents written by Christian Ankerstjerne unless stated otherwise