A few Panzer IIIs, largely the early models though including some Ausf E, had their baptism of fire in Poland in 1939. ‘In this campaign the quality of our materiel left much to be desired,’ wrote Major-General Friedrich von Mellenthin. ‘We only had a few Mark IVs with low velocity 75mm guns, some Mark IIIs carrying the unsatisfactory 37mm, and the bulk of our armoured strength was made up of Mark IIs carrying only a heavy machine gun.’
Guderian, by now a corps commander, insisted the Panzer Lehr Battalion that had the new Panzer III and IV be included in his 19th Corps for the invasion of Poland. This was a training unit but he was determined that they test out their panzers and tactical theories under combat conditions. Because both tanks were armed with shortbarrelled guns, they offered an indifferent anti-tank capability. Fortunately for the Germans, the Polish Army’s own tanks were little more than reconnaissance vehicles, making the panzers shortcomings of little significance.
Hitler visited Guderian in Poland to find out how the new panzers had performed. Guderian informed the Führer that their speed was fine but they needed better armour and guns. ‘I told him,’ wrote Guderian ‘that the most important thing now was to hasten the delivery of the Panzer III and IV to the fighting troops and to increase production of these tanks’, points which Hitler took on board. It was shortly after the Polish campaign came to an end that the Panzer III and IV were accepted as the standard equipment of all the tank battalions.
At the start of the campaign in the West in May 1940 a total of 349 Panzer IIIs and 278 Panzer IVs formed the core of the attack. There were also thirty-nine Panzer III command vehicles supporting them. Hitler fielded an overall force of 2,574 tanks. In France the Panzer III proved inadequate against the heavier British and French tanks. The Germans’ ready solution to this was using their flak guns in an anti-tank role and calling on their heavy artillery and dive bombers to deliver high explosives. Rommel was to repeat this highly successful tactic in North Africa.
In contrast, some 3,200 panzers were ready for the invasion of the Soviet Union in the summer of 1941 with a high proportion of this number being Mk IIIs. By this point the 50mm gun had been introduce into the Panzer III, with the progressive replacement of the 37mm gun in existing vehicles, and as the standard weapon of the new ones being built from the latter part of 1940 onwards.
During the invasion of France, whilst commanding the 7th Panzer Division, Rommel became only too familiar with the capabilities of the Panzer III and IV. He almost lost his life in a Mk III. For the breakthrough on the River Meuse he directed operations from inside one. He does not relate whether he replaced the tank commander or whether he and the five crew were all squeezed into the tank together. Once on the move, his Panzer III was hit twice, once on the upper edge of the turret and once in the periscope. A splinter from the shell that hit the periscope wounded Rommel in the right cheek and he bled profusely. He could have lost an eye or even been killed. Trying to evade French artillery and anti-tank fire, the driver accidently slid the tank down a steep bank, where it became stuck on its side and dangerously exposed. Unable to rotate the turret, Rommel and the crew bailed out and only just escaped to safety. Rommel also briefly employed a Panzer III as an escort for his command vehicle at Le Câteau until it suffered mechanical problems. At Arras his tanks received a nasty surprise at the hands of the British Matildas. Rommel lost six Panzer IIIs and three Panzer IVs, but quickly restored the situation by deploying his artillery to support his tanks.
Had Operation Sealion and the invasion of England taken place, the Panzer III would have played a prominent role. Ultimately though, getting the panzers ashore was an insurmountable problem at the time. The war correspondent and historian Chester Wilmot observed that ‘the Germans would not have been able to land tanks in large numbers until they had captured and opened ports on the southeast coast. At the end of August  the Wehrmacht had available for landing from the sea only 42 Mark IVs and 168 Mark IIIs.’ It was simply not enough.
The Panzer III was the most widely-deployed German tank spearheading Rommel’s operations in North Africa, outnumbering the Panzer IIs and IVs by two to one. Until early 1942 the most potent versions available were the Ausf F, G and H with the 50mm L/42 gun. This was capable of penetrating 45mm of homogenous armour plate sloped at 60° at its effective range of 750 yards
The 5th Light Division’s (later 21st Panzer) 5th Panzer Regiment began landing in Tripoli in mid-February 1941, bringing with it an official tank strength of 165, comprising seventy Panzer I and IIs, seventy-five Panzer IIIs and twenty Panzer IVs. Beforehand, the division suffered a mishap in Naples where a cargo ship caught fire and sank with the loss of ten Panzer IIIs and three Panzer IVs. Rommel was fortunate to get the rest ashore unscathed, as shortly afterwards the RAF bombed Tripoli. In one attack on the harbour an ammunition ship was hit and exploded, destroying an entire block of buildings. This good fortune was of Rommel’s own making as he had insisted the tanks be unloaded during the night.
The replacements for the 5th Panzer Regiment did not reach them until the end of April. The 15th Panzer Division’s 8th Panzer Regiment was shipped to Libya in three convoys between 25 April and 6 May 1941. This unit initially fielded 146 tanks, comprising forty-five Panzer II, seventy-one Panzer III, twenty Panzer IV and ten command tanks.
The Panzer IIIs’ first role in Tripoli was to take part in a show of force and an act of duplicity on 15 February 1941. Rommel instructed ‘The moment every panzer is unloaded, the German 5th Panzer Regiment and the tanks of the Italian Ariete Division will parade in a fashion that will not escape the attention of, first the Italian civil population, and second the enemy’s spies. . . . On completion of the paraded the regiment will immediately proceed to the front . . .’
When the parade commenced having rolled down the main street they turned into a side street and circled back to create the impression that there were more panzers than there really were. Lieutenant Heinz Schmidt, who was on Rommel’s staff, was highly amused by the subterfuge when he realized one of the tanks ‘somehow looked familiar to me although I had not previously seen its driver. Only then did the penny drop, as the Tommies say, and I could not help grinning. Still more panzers passed, squeaking and creaking round that bend.’
German observers were disappointed by the Italian crowd’s complete lack of enthusiasm and utter silence. Tripoli’s officials cannot have been pleased that the panzers’ tracks were chewing up the road surface. It was only when the slower moving Ariete Division appeared that they began to cheer. The British, on the other hand, were suitably alarmed by the news of Rommel’s arrival.
Initially the Panzer III’s chief opponent in North Africa was the British Cruiser Mk IV (A13 Mk II), armed with the 2-pounder (40mm) gun capable of piercing 40mm of armour at the same range as the L/42. As neither tank had armour in excess of 30mm and as both had comparable speeds, they were largely evenly matched. Rommel was impressed by the Cruiser Mk VI Crusader which appeared in June 1941 as it was better armoured and much faster. Once again, however, it was only armed with the 2-pounder gun and at first proved very mechanically unreliable. It was later upgunned with a 6-pounder (57mm) gun.
Rommel’s Panzer III crews were photographed in the desert wearing a tropical sun helmet, called the Tropische Kopfbedeckung, which was issued to the Afrika Korps in early 1941. This was stowed on the outside of the turret because it was simply not practical to wear it inside the tank. Not surprisingly the crews soon abandoned them in favour of the more comfortable field cap and even captured South African Army sun helmets that were smaller (though they still ended up hung on the outside of the turret).
To fend off the British summer offensive in 1941, Rommel only had ninety-five Panzer IIIs and IVs. By the time of Operation Crusader, launched by the British on 18 November 1941, he could muster about 139 Panzer IIIs, but half of them were still armed with the 37mm gun, and just thirty-five Panzer IVs.
Views on the Panzer III’s performance differed greatly on either side. Mellenthin, who served as a staff officer with the Afrika Korps, recalled:
The Mark III used by the Panzergruppe in the Crusader battle only mounted a low-velocity 50mm gun, which British experts now admit had no advantage over their 2-pounder gun. Nor did we have any advantage in the thickness of armour. The British heavy infantry tanks – Matilda and Valentine – completely outclassed us in that respect, and even the Crusaders and Stuarts were better protected than our Mark III. For example the maximum basic armour of the Mark III in the Crusader battle was 30mm, while the Crusader nose and hull fronts were protected by 47mm, and the Stuart had 44mm protection there.
Interestingly, after talking to a British tank commander, the war correspondent Alexander Clifford took a very different view:
The Mark IIIs and Mark IVs both had more fire-power than anything we had got. We found ourselves up against the Mark IIIs’ 50mm guns firing four-and-a-halfpound shells and the Mark IVs’ definitely heavier type. It was like pitting destroyers against cruisers. It meant that the British had to start every battle with a sprint of half a mile under fire before they could fire back.
He calculated that 100 panzers could claim thirty British tanks before they could even get in range to engage. ‘It was absurd to pit British and American tanks with their 37mm guns against the Mark IIIs with their 50mm and the Mark IVs with their 75mm weapons and pretend that the terms were equal,’ concluded Clifford. ‘To do so was grossly unfair to our armoured brigades.’