"T-1 tank
The driver's observation devices are located in the turret platform. There are two slits in the observation hatch in front of the driver. For observation hatches are located in the corners of the turret platform. The slits in the hatches on the left side are covered with two layer protective glass. There are no slots in the right side. The driver observes through the front slits and the left slit.
The commander observes through the machine gun sight. Outside of battle, he can use the observation ports above the machine guns. Observation ports without slits are located on the sides of the turret. Two observation ports with slits are located in the back of the turret. The location and range of the devices is shown in figure 15. The observation devices do not protect the observer. It is impossible to observe to the right during battle.
Figure 15: T-1 tank. Dead zones: driver - 4.6 m (front slit), 3.7 m (left slit). Turret: 5.9 m.
T-2b
Observation devices are located in the turret platform. An observation slit is located in front of the driver. The slit is covered by five layer protective glass. Observation ports with slits are located to the left and right of the driver. The slits are covered with protective glass from the inside.
The turret crewman can observe from either the sights or two observation ports pointing forward. There are two observation ports to the right side of the turret. The front has no slit, the rear has a standard slit with protective glass. There is an observation port with a slit to the rear. An immobile commander's cupola is located on the turret. There are eight mirror periscopes in the turret. As the diagram (figure 16) shows, there are more observation devices than on the T-1, but they are insufficiently reliable.
Figure 16: T-2b tank. Dead zones: driver - 4.65 m (front slit), 4.2 m (side slits), 11 m (rear). Turret - 4.2 m.
T-3
The driver of the T-3 tank can see forward and to the left. Forward observation is performed through a slit. The slit is protected with five layer protective glass. There is a backup binocular telescope sight. An observation port with a slit is located to the left. The hull gunner located to the right of the driver only observes through the machine gun sight.
Two observation ports are present in the gun mantlet, the left, and the right sides of the turret. The right port in the mantlet has a slit with protective glass. The side ports also have slits with protective glass.
A commander's cupola is installed on the turret with five slits around its circumference. The width of the slits can be changed with armoured shutters. The slits are covered with five layer protective glass. The location of the observation devices and their range is shown in figure 17.
Figure 17: T-3 tank. Dead zones: driver - 3.5 m (front slit), 5.4 m (left slit). Turret - 11.5 m (slits), commander's cupola - 7 m (large slit), 24 m (small slit).
T-4
The driver observes through a front observation slit. The slit is covered with protective glass from the inside and has an armoured shutter on the outside. There is an observation port to the left with a slit protected by glass. There is an observation port with a slit to the right, near the hull gunner.
Forward observation from the turret is performed via the sights or the observation port. Entrance hatches have observation slits protected by glass. The immobile commander's cupola has five slits. Like on the T-3, the width can be changed. All slits are covered with protective glass.
Compared to the T-3 tank, the gunner's vision is improved. The number of ports without slits is reduced. The driver has no backup sight. Observation angles and ranges are shown in figure 18.
Figure 18: T-4 tank. Dead zone: driver - 3 m (front slit), 5.4 m (left slit), 5.4 m (right slit). Turret - 14 m (slit), commander's cupola - 7 m (large slit), 24.5 m (small slit).
T-5 tank (Panther)
The driver has a mirror observation periscope and an observation port protected by glass. The same observation periscope is installed to observe to the left.
The hull gunner has two mirror observation periscopes like the driver.
In addition to the sights, the turret crew can only see through hatches.
The commander's cupola is immobile. It has six slits protected by glass. The observation range is shown in figure 19. The latest Panther tanks have cast commander's cupolas with periscopes instead of slits.
Figure 19: T-5 tank. Dead zones: driver - 7 m (slit), 9.5 m (periscope). Commander's cupola - 15 m.
T-6 tank (Tiger)
The driver observes through an observation slit or a mirror periscope. The slit is located in the front of the hull and is covered with protective glass. The periscope is in front of the driver in his hatch. The hull gunner observes through the same periscope.
There are two observation slits on the sides of the turret.
There is an immobile commander's cupola with six slits. The slits are closed with protective glass. The observation range of the T-6 is given in figure 20. The latest T-6 tanks have a cast commander's cupola with seven mirror periscopes.
Figure 20: T-6 tank. Dead zones: driver - 6 m (slit), 9 m (periscope). Turret - 11 m (slit). Cupola - 16 m.
38-T tank
There is an observation slit in front of the driver. There is an observation periscope in the turret platform to the right. The hull gunner observes through a slit. There is no way to look to the left or backwards. There is no vision from the turret, only the sights can be used. There is a commander's cupola on the main turret. There are four mirror periscopes in it. The front periscope is the main one and has a different design.
The observation devices have no backups and no shutters. The driver and hull gunner's vision is limited.
Somua tank
The driver has three observation slits: one forward and two to the sides. The slits are covered with two layer protective glass. Another slit is located in the front armour to the right.
Observation from the turret is possible only through the gun sights and two slits. The slits are covered with two layer glass.
A rotating commander's cupola is located on the main turret. The cupola has four slits. A drawback of the cupola is the mismatch of the slit width and protective glass thickness.
Renault tank
The driver can only observe through the hatch with a slit. Either a large or a small slit can be set. The large slit is covered with two layer protective glass. Slits with armoured shutters are located to the left and right.
Observation slits are located in the sides of the turret. Presumably the Germans installed mirror observation devices from the 38-T tank here.
The rotating cupola only has one slit. The slit is covered with a shutter from the outside, there is no protective glass. The Renault tank has many poorly protected slits. The front observation hatch design with dual slits is bulky and poor.
Landsverk tank
Mirror observation devices are located in front of the driver and to his sides. Backup observation ports are also available next to them.
In addition to the sights, there are observation ports in the turret: one to the left and two to the right.
There are five mirror observation devices and two observation ports in the cupola.
The number of observation devices on the tank is high, but their design does not allow for safe observation.
L-6 tank
The Italian light L-6 tank has a crew of two. The driver has a slit in an observation hatch and a mirror periscope on the roof of the turret platform. The slit is located in a cylinder, which can be turned to close it. The driver can't see to the left and right. The turret crewman can only observe through the gun sight.
Summary
Only German tanks are worthy of attention of all captured tanks. French, Czech, Italian, and other tanks are usually equipped with just poorly protected vision slits. The existing observation devices are complicated and unreliable. The use of observation cupolas is common, but the primitive and unreliable design of the cupolas and their observation devices makes them ineffective.
In German tanks, the T-1 has unsatisfactory observation, but improvement can be observed. All tanks after the T-2b have a commander's cupola. The T-5 and T-6 have a reduced number of observation hatches and slits. Vision is improved, a backup observation device for the driver is installed and observation devices for the hull gunner are also introduced.
Recent tanks received mirror observation devices (before this seen only on the T-2 and 38-T). Slits in commander's cupolas are replaced with mirror periscopes.
The observation devices of captured tanks (T-3, T-4, T-5, T-6) are sufficient and can be used safely.
Conclusions
- The best observation device is the MK-4 mirror periscope with a pivoting mount with a reversible mirror.
- This type of periscope should be given to each crewman, including the radio operator.
- Observation slits protected by glass can be used as backup vision devices in main directions.
- Drivers in light tanks need two devices, a periscope and a slit. Drivers in medium tanks need three: two periscopes and a slit.
- All openings for observation should have armoured shutters.
- The commander of a light tank can have a rotating periscope. Commanders of medium and heavy tanks should have immobile observation cupolas.
- When placing the observation devices, keep in mind the configuration of the hull and protruding elements, as observation angles can be reduced if it is installed incorrectly."