Rommel had also had an offensive plan in mind. Aware that one day 8th Army, massively reinforced and equipped, would come storming out of the desert in a drive for victory the German commander's only hope for his command was to strike a pre-emptive blow. Every hour was precious and only by concentrating and then striking to the east would there be a chance to defeat the British. But first the ulcer of Tobruk would have to be taken out and then, with Cunningham's force defeated, the advance upon the Suez canal could begin. Bastico, the local commander, approved the plan but made the proviso that the offensive was not to begin until forces, sufficient in strength to guarantee success, had been built up. During the second week in November the strength of Panzer Army Africa and that of its ally had reached that peak and Rommel, beginning to plan in detail, decided that his attack should begin on or about 21 November.
The Axis forces held a battle line which had, in the east, an enclave that reached from the town of Bardia down to the Halfaya Pass and included within the perimeter the town of Sollum. The whole area was garrisoned by Savona Division and two German units. The Axis forces investing Tobruk, on the western flank, were mainly Italian: Brescia, Pavia, Trento, and Bologna Divisions; with the German Special Services Division, which was to be retitled during the fighting and which has passed into military history as the 90th Light Division.
The 15th Panzer Division was moved from its holding position near Tobruk to a forming-up area on either side of Sidi Belafarid. The 21st Panzer Division (the new name for the old 5th Light Division) held the middle ground, along the Trigh Capuzzo, midway between Tobruk and Bardia. To the south-east of the 21st Panzer the 3rd Reconnaissance Battalion and to the south-west the 33rd Reconnaissance Battalion, screened the desert against a British move. Protecting the south of the Axis line, at Bir el Gobi, was Ariete Division while in deep echelon, either as a reserve or as a counter-attack formation was Trieste Division, in position around Bir Hachim.
To protect the Panzer Army's forming-up area, should 8th Army's expected assault come in early or even meet the advance of the Axis force head-on, 21st Panzer Division would intercept east of Tobruk and once that fortress had been taken the whole Axis army would crash like a giant fist towards and across Egypt.
Lacking aerial reconnaissance reports the Germans were forced to build up a mosaic of British intentions and strengths through the reports of their own weak and scattered armoured car reconnaissance patrols, but these were neither enough in number nor sufficiently widespread in area to enable the staff to assess accurately British intentions. By 16 November there had been patrol clashes and during 18th the Africa Corps headquarters had been sent a report that a British column was moving northwards from Giarabub, but this manoeuvre was dismissed as a mere reconnaissance and the build-up to the Tobruk assault was maintained. German patrols had not located those units from 8th Army which had reached the heights between Sidi Omar and Gabr Saleh and reports that German patrols had clashed with British armoured cars along the Trigh el Abd seem neither to have been received at headquarters nor, if they were received, to have been acted upon.
The British offensive opened under a massive air umbrella and the men and tanks of 8th Army crossed the frontier wire and began to move upon Tobruk. Operation Crusader was opened by an advance of the armour which struck in a three-pronged drive across the area from Gabr Saleh (4th Brigade) and Bir el Gobi (22nd Brigade). These two brigades also had flank duties — that of 4th Brigade to guard the 13 Corps wing, while 22nd Brigade was to secure the open southern flank. The 7th Brigade, in the centre, had as its objective the area of, and around, Sidi Rezegh. This wide open formation held the seeds of the severe losses which the British were to suffer in the next few days for the columns were too far apart to give each other mutual support, and that direct and immediate command system under which the panzer formations were controlled was missing. The British brigades were to be flung piecemeal into battle and destroyed piecemeal although, in the initial stages of the operation, the wide front over which they were dispersed had the advantage that the Germans thought themselves to be facing stronger armoured forces than was the case, and, also, they were not able to identify immediately where the main British thrust would come.
On the British eastern flank 4th Brigade's 3rd Royal Tank Regiment reached to within 15 miles of Gabr Saleh and there, meeting elements from 3rd Reconnaissance Battalion, engaged these and drove them northwards. The 7th Brigade struck towards Sidi Rezegh and met little or no opposition en route, but then having reached its given objective, halted and consolidated. During the afternoon of 19 November a group of 60 tanks from 22nd Brigade in the area of Bir el Gobi met, struck, and drove off the Ariete Division, smashing the obsolescent tanks with which the Italian Armoured Division was equipped. Five British tanks fell victim to the Italian artillery.
At midday on 19th the battle situation was still unclear to the Axis commanders. The British had achieved a complete tactical surprise and it was to be 48 hours before Rommel knew the might and direction of the assault, although a prisoner from 4th Indian Division had been interrogated and had given his captors full details of the British plan. The hitherto unknown fact that 7th Armoured Division had crossed from Egypt into Libya was supplied to the Germans but this accurate information was not believed by Panzer Group, which was still of the opinion that this was no major offensive but a raid in strength despite confirmatory evidence. The 33rd Reconnaissance Battalion had reported that an armoured force, estimated to be in divisional strength, was heading towards Tobruk and an air reconnaissance had confirmed three British columns, part of 1st Army Tank Brigade and 1st South African Division, between Giarabub and Bir el Gobi.
The 21st Panzer Division was ordered to attack and to destroy the British units which were believed to be reconnaissance forces and located in the area between Sidi Omar and Gabr Saleh. The 15th Panzer which had moved up during that afternoon, to the west of 21st Panzer, moved in a four-column formation to take up position in the area west of Gambut and had reached its specified area by 21.00hrs.
To undertake the mission of destroying the so-called British reconnaissance forces the 21st Panzer Division formed Battle Group Stephan. The armoured brow of the battering ram which would scatter the weak enemy group was made up of 110 tanks from 5th Panzer Regiment and artillery from 2nd Battalion 155th Artillery Regiment as well as 3rd Battalion of 18th Flak Regiment. This advance guard was closely followed by the main of the division. Moving forward in a solid phalanx the battle group drove at a fast pace across the desert and at about 15.30hrs crashed into 4th Tank Brigade a: a point some 5 miles north-east of Gabr Saleh. This attack by the divisional battle group was a calculated risk for it was advancing deep into the British flank with its own flanks unprotected.
As the armoured forces clashed the crews of the powerful 8.8cm guns formed a gun line and took the British tanks under fire at ranges greater than those at which the Stuart tanks could retaliate. Under the double punch of the high velocity 8.8cm and the 5cm and 7.5cm tank guns, the British brigade was hurled back across the Trigh el Abd. But the British armour reformec and came on again, again, and yet again. In the fighting which lasted unti dusk 42 Stuarts were destroyed or fell out for the loss of three of the panzer force. The German tank recovery teams were soon in action and even in the heat of battle began to recover some of those Stuarts which had been abandoned. At last light the British withdrew from the battlefield and thus out of contact with 21st Panzer, leaving that unit laagered east of Gabr Saleh.