The mountainous Benning Range, like a towering screen on the border between England and Scotland, is characterized by exposed limestone and lava terrain, with only a few mountain passes accessible by roads, making it easily defensible. In early 1941, a portion of the British forces retreating from the north of England sought refuge in the mountains, intending to hold their ground based on the terrain. However, the advancing German forces did not commit significant troops here. Their armored divisions flowed through the valleys of the Trent River to the south and the South Tyne River to the north of the range, swiftly advancing into the lowlands of southern Scotland. Despite sporadic attacks by British guerrilla forces on German logistical supply lines in the valleys, once the British lost air and sea superiority, they were unable to halt the German main forces' advance toward Edinburgh and Glasgow.
February 17, 1941, Edinburgh.
To cover the evacuation of the last personnel from the sea, a rear guard force of six infantry regiments, one artillery regiment, and an independent tank company (in the book's setting, due to a shortage of tanks, the British later consolidated their remaining tanks into several independent tank companies for defensive operations in strategic locations) engaged in fierce combat with the leading units of the German 12th Armored Division and the 36th Motorized Infantry Division in the southern outskirts.
As one of the ten armored divisions newly formed after the end of the French campaign, the German 12th Armored Division was primarily equipped with the 38(t) as its main battle tank. In addition to over a hundred light tanks originally from Czechoslovakia, the division was equipped with around 30 command-type IV tanks and approximately 70 I and II tanks, with overall combat strength comparable to the early German armored divisions. However, they encountered extremely stubborn resistance from the British in the Edinburgh suburbs. In the battle, over 20 tanks were destroyed by American-made 37mm anti-tank guns used by the British artillery. What impressed the Germans the most was the "Matilda II" modified with 6-pounder infantry guns. The 57mm caliber guns, when firing armor-piercing shells, could penetrate any tank equipped by this German armored division at a distance of 800 meters. Although victory in the Battle of Edinburgh was ultimately won through skillful tactical coordination, German commanders meticulously reported the difficulties their troops encountered on the battlefield to their superiors!
On the same day, the Battle of Glasgow began, with the German 22nd Airborne Division conducting airborne operations in the northwest and southwest suburbs of the port city, intending to quickly seize the various shipyards there. Meanwhile, the German 13th and 16th Armored Divisions, along with a motorized infantry division, three regular infantry divisions, and the group artillery, launched a fierce attack on the British defensive line about 20 kilometers south of Glasgow.
In the early urban combat led by the German airborne forces, despite the full cooperation of the gliders carrying the III and IV tanks, more than half of them were destroyed by the anti-tank weapons used by the British. After the battle, the German soldiers were surprised to find that one of their III tanks had been penetrated by more than a dozen large-caliber anti-tank bullets, resulting in casualties or injuries to the entire crew! In addition, the British infantry's 2-pounder (40mm) and 6-pounder (57mm) guns could effectively threaten German airborne tanks in close and medium-range combat!
Outside Glasgow, although the usually unstoppable German armored forces broke through the British defensive line in just five hours, both armored divisions, mainly equipped with II and III tanks, suffered casualty rates exceeding fifteen percent. In the assault, the weakness of German tank armor was blatantly exposed due to the British employing various anti-tank weapons, resulting in many tanks being destroyed or damaged by anti-tank guns, flamethrowers, infantry anti-tank explosives, and anti-tank rifles!
Capturing Edinburgh in 21 hours and seizing Glasgow in 26 hours, the strong advance of the German forces in the Battle of Britain largely concealed the shortcomings in tank performance. Moreover, in response to the demands of the German High Command and Army, major arms manufacturers were rushing to produce III and IV tanks, but the monthly output was still less than 650 units—making it unrealistic to quickly equip the large armored formations of the army with new tanks!
Fortunately, not everyone was complacent and satisfied with the status quo. Just a day after the battles of Edinburgh and Glasgow ended, in the suburbs of Berlin at the Kummersdorf testing ground, the German Air Force conducted the first prototype display of the "35-ton airborne tank" that it had commissioned from various arms companies in the early stages. After preliminary selection, Rheinmetall's design proposal was bleakly eliminated, while the proposals from Krupp, Daimler-Benz, and the veteran arms company Henschel were all validated, and they had each developed the first prototype!
Logically, it was too hasty to develop a medium tank from scratch in just half a year. Therefore, when the initial order was issued, the German Air Force requested that various arms companies use as many components from the III and IV tanks as possible, striving to complete the prototypes by spring 1941.
As the planner of the "35-ton airborne tank" project, Logan, who had already served as the Chief of Air Force Operations, personally attended the event. Drizzling rain fell from the sky, and on the open space of the test ground, four tanks of different sizes and appearances were lined up. The one parked furthest to the right was the IV F2 tank, already being deployed by both the Waffen-SS and the Wehrmacht. With a combat weight of 26 tons, it was visibly smaller than the other three. Its distinctive feature was the 43-caliber 75mm long-barreled gun, which distinguished it from previous IV tanks. Additionally, its turret was welded with spaced steel plates and a steel lattice, while steel skirts were installed on both sides of the hull. This design had already been proven effective on the British battlefield, and judging by the feedback from the troops, it worked quite well!
From left to right, the prototypes from Krupp, Daimler-Benz, and Henschel were displayed. At first glance, Krupp's "35-ton tank" was simply an enlarged version of the IV tank, with a distinct square turret and boxy body shape. Apparently, the designers did not pay much attention to the Air Force's request for "turret and body inclination" in the order—according to the performance data manual, the body inclination was listed as "85°", almost negligible!
Daimler-Benz's prototype, with a wider and shorter body compared to Krupp's, clearly prioritized the power system. It featured a 600-horsepower diesel engine manufactured by Daimler-Benz, theoretically capable of reaching a maximum highway speed of 55 kilometers per hour, with a maximum highway range of over 300 kilometers. In terms of these two performance metrics alone, it far surpassed any existing German tanks, with the body and turret inclination ranging between 75 and 80 degrees. When Logan saw the detailed introduction in the data manual, he immediately harbored high expectations for this tank. However, if he were to learn that Daimler-Benz opted for a diesel engine over a gasoline engine primarily due to the limited supply of diesel for airborne tank purchases, and if there wouldn't be too much trouble in diesel supply, Logan might have felt even more keenly aware of the significance of oil regions like Baku and the Persian Gulf.
In addition to pioneering the use of onboard diesel engines, Daimler-Benz also equipped their prototype with a spring suspension system. Considering the characteristics of airborne operations, they reinforced the tank's seismic resistance structure, a move that impressed the technical experts of the Air Force!
As for the last prototype from Henschel, it retained the traditional square body of German tanks, and the so-called inclination was just a "visual effect of 85 degrees." To make the turret, fitted with a long-barreled 75mm gun, more operationally practical, they specially designed a turret wider and longer than that of the Panzer IV. From a cross-sectional perspective, this welded turret structure took on a semi-elliptical shape and added a scoop-shaped shield, enhancing defense by more than eighty percent compared to the Panzer IV. Concerning the engine, considering that airborne tanks would be carried by transport aircraft, they innovatively opted for the Jumo 205 diesel engine used in the Ju-86 aircraft. Given the size of tank engines, they ultimately installed a modified 6-cylinder aviation diesel engine on their prototype, providing 720 horsepower at 1700 rpm, allowing it to achieve a remarkable speed of 60 kilometers per hour even when weighing 1.8 tons more than the Daimler-Benz prototype. Furthermore, Henschel's engineers considered that despite using lightweight aviation fuel, this type of diesel engine could easily obtain fuel from Air Force bases and even some transport aircraft tanks!
Typically, prototypes are not subjected to comprehensive tests like later-stage assessments of mobility, defense, attack capabilities, and long-distance reliability. Moreover, due to the short preparation time, some components of the three prototypes used "substitutes" of equivalent weight or similar utility. Therefore, German officers and technical experts circled around them like exhibits in a museum, listening to the main engineers explain the performance of their respective prototypes. Next, in a highly anticipated event, both Krupp and Daimler-Benz conducted manned trials of their prototypes. Logan personally sat on the turret to feel the difference between the "35-ton airborne tank" and the Panzer IV. Overall, Krupp's prototype demonstrated the most mature technology, completing two laps around the test field without any faults, while Daimler-Benz's diesel engine stalled three times during the tank's movement, exhibiting the characteristic of emitting black smoke and loud noise. As for Henschel's innovative aviation diesel engine, due to the need for technical improvements, it ultimately failed to undergo practical demonstration.
After the exhibition, under the chairmanship of Air Force Deputy Commander Milch, the Air Force Weapons Production Department, Airborne Equipment Department, and Air Force Operations Department held a "tri-departmental review." Most officers leaned toward Krupp's prototype, considering its relatively mature technology that could enter mass production smoothly in a few months. On this issue, Logan once again exerted his subjective influence: each of the three companies' prototypes had its own characteristics, yet none passed the armor test. Upon his strong recommendation, all three arms manufacturers were granted orders to produce three test vehicles each, contingent upon corresponding improvements in armor inclination, armor thickness, and engine stability!
In terms of cost, the unit prices quoted by arms dealers exceeded three times that of the Panzer IV production model—many officers felt it would be better to directly modify the Panzer IV. However, Logan remained steadfast in his belief that the present cost would soon demonstrate its enormous value!