On 8 April, the Yugoslav vanguard, the "Komski" Cavalry Regiment crossed the treacherous Prokletije Mountains and captured the village of Koljegcava in the Valjbone River Valley, and the 31st "Kosovska" Division, supported by Savoia-Marchetti S.79K bombers from the 7th Bomber Regiment of the Royal Yugoslav Air Force (VVKJ), broke through the Italian positions in the Drin River Valley. The "Vardarska" Division, due to the fall of Skopje was forced to halt its operations in Albania. In the meantime, the Western Macedonia Army Section under General Tsolakoglou, comprising the 9th and 13th Greek Divisions, advanced in support of the Royal Yugoslav Army, capturing some 250 Italians on 8 April.
The Greeks were tasked with advancing towards Durrës. On 9 April, the Zetska Division advanced towards Shkodër and the Yugoslav cavalry regiment reached the Drin River, but the Kosovska Division had to halt its advance due to the appearance of German units near Prizren. The Yugoslav-Greek offensive was supported by S.79K bombers from the 66th and 81st Bomber Groups of the VVKJ, that attacked airfields and camps around Shkodër, as well as the port of Durrës, and Italian troop concentrations and bridges on the Drin and Buene rivers and Durrës, Tirana and Zara.
Between 11–13 April 1941, with German and Italian troops advancing on its rear areas, the Zetska Division was forced to retreat back to the Pronisat River by the Italian 131st Armoured Division Centauro, where it remained until the end of the campaign on 16 April. The Italian armoured division along with the 18th Infantry Division Messina then advanced upon the Yugoslav fleet base of Kotor in Montenegro, also occupying Cettinje and Podgorica.
The Yugoslavs lost 30,000 men captured in the Italian counterattacks.
The Metaxas Line was defended by the Eastern Macedonia Army Section, which comprised the 7th, 14th and 18th Infantry Divisions under the command of Lieutenant General Konstantinos Bakopoulos. The line ran for about 170 kilometres (110 miles) along the river Nestos to the east and then further east, following the Bulgarian border as far as Mount Beles near the Yugoslav border. The fortifications were designed to garrison over 200 000 troops, but the actual number was roughly 70 000. As a result, the line's defences were thinly spread. Some 950 men under the command of Major George Douratsos of Major-General Konstantinos Papakonstantinou's 14th Division defended Fort Rupel.
The Germans had to break the line to capture Thessaloniki, Greece's second-largest city, with a strategic port. The attack started on 6 April with one infantry unit and two divisions of the XVIII Mountain Corps. Due to strong resistance, the first day of the attack yielded little progress in breaking the line. A German report at the end of the first day described how the German 5th Mountain Division "was repulsed in the Rupel Pass despite strongest air support and sustained considerable casualties". Two German battalions managed to get within 600 feet of Fort Rupel on 6 April, but were practically destroyed.
Battle of the Metaxas Line
Of the 24 forts that made up the Metaxas Line, only two had fallen and then only after they had been destroyed. In the following days, the Germans pummelled the forts with artillery and dive bombers and reinforced the 125th Infantry Regiment. A 7 000 foot (2100 meter) high snow-covered mountainous passage considered inaccessible by the Greeks was successfully crossed by the 6th Mountain Division, which reached the rail line to Thessaloniki on the evening of 7 April. The 5th Mountain Division, together with the reinforced 125th Infantry Regiment, penetrated across the Struma river under great hardship, attacking along both banks and clearing bunkers until they reached their objective location on 7 April. Heavy casualties caused them to temporarily withdraw.
The 72nd Infantry Division advanced from Nevrokop across the mountains.
Its advance was delayed by a shortage of pack animals, medium artillery and mountain equipment. Only on the evening of 9 April did it reach the area northeast of Serres. Most fortresses - like Fort Roupel, Echinos, Arpalouki, Paliouriones, Perithori, Karadag, Lisse and Istibey - held until the Germans occupied Thessaloniki on 9 April, at which point they surrendered under General Bakopoulos' orders.
Nevertheless, minor isolated fortresses continued to fight for a few days more and were not taken until heavy artillery was used against them. This gave time for some retreating troops to evacuate by sea.
Although eventually broken, the defenders of the Metaxas Line succeeded in delaying the German advance.The Metaxas Line, requiring 150,000 men, could have held out longer, but the bulk of the Greek army was facing the Italians in Albania.
The dispositions of forces in the Florina Valley, 10 April 1941. The blue arrows indicate German advances and the Allied lines are shown in red. Vevi and the Klidi Pass are upper centre, the Australian 19th Brigade HQ is in the centre and Mackay Force HQ is at Perdika, lower centre.
The XXX Infantry Corps on the left wing reached its designated objective on the evening of 8 April, when the 164th Infantry Division captured Xanthi. The 50th Infantry Division advanced far beyond Komotini towards the Nestos river. Both divisions arrived the next day. On 9 April, the Greek forces defending the Metaxas Line capitulated unconditionally following the collapse of Greek resistance east of the Axios river. In a 9 April estimate of the situation, Field Marshal List commented that as a result of the swift advance of the mobile units, his 12th Army was now in a favorable position to access central Greece by breaking the Greek build-up behind the Axios river. On the basis of this estimate, List requested the transfer of the 5th Panzer Division from First Panzer Group to the XL Panzer Corps. He reasoned that its presence would give additional punch to the German thrust through the Monastir Gap. For the continuation of the campaign, he formed an eastern group under the command of XVIII Mountain Corps and a western group led by XL Panzer Corps.
By the morning of 10 April, the XL Panzer Corps had finished its preparations for the continuation of the offensive and advanced in the direction of Kozani. The 5th Panzer Division, advancing from Skopje encountered a Greek division tasked with defending Monastir Gap, rapidly defeating the defenders. First contact with Allied troops was made north of Vevi at 11:00 on 10 April. German SS troops seized Vevi on 11 April, but were stopped at the Klidi Pass just south of town, where a mixed Empire-Greek formation - known as Mackay Force - was assembled to, as Wilson put it, "...stop a blitzkrieg down the Florina valley." During the next day, the SS regiment reconnoitered the Allied positions and at dusk launched a frontal attack against the pass. Following heavy fighting, the Germans broke through the defence. On 13 April, 70 supporting German bombers attacked Volos, the port almost being completely destroyed. By the morning of 14 April, the spearheads of the 9th Panzer Division reached Kozani.
Wilson faced the prospect of being pinned by Germans operating from Thessaloniki, while being flanked by the German XL Panzer Corps descending through the Monastir Gap. On 13 April, he withdrew all British forces to the Haliacmon river and then to the narrow pass at Thermopylae. On 14 April, the 9th Panzer Division established a bridgehead across the Haliacmon river, but an attempt to advance beyond this point was stopped by intense Allied fire. This defence had three main components: the Platamon tunnel area between Olympus and the sea, the Olympus pass itself and the Servia pass to the south-east. By channeling the attack through these three defiles, the new line offered far greater defensive strength. The defences of the Olympus and Servia passes consisted of the 4th New Zealand Brigade, 5th New Zealand Brigade and the 16th Australian Brigade. For the next three days, the advance of the 9th Panzer Division was stalled in front of these resolutely held positions.
British vechiles destroyed, greece 1941
A ruined castle dominated the ridge across which the coastal pass led to Platamon. During the night of April 15, a German motorcycle battalion supported by a tank battalion attacked the ridge, but the Germans were repulsed by the 21st New Zealand Battalion under Colonel Macky, which suffered heavy losses in the process. Later that day, a German armoured regiment arrived and struck the coastal and inland flanks of the battalion, but the New Zealanders held. After being reinforced during the night of the 15th - 16th, the Germans assembled a tank battalion, an infantry battalion and a motorcycle battalion. The infantry attacked the New Zealanders' left company at dawn, while the tanks attacked along the coast several hours later.The New Zealanders soon found themselves enveloped on both sides, after the failure of the Western Macedonia Army to defend the Albanian town of Koritsa that fell unopposed to the Italian 9th Army on 15 April, forcing the British to abandon the Mount Olympus position and resulting in the capture of 20,000 Greek troops.
Australian anti-tank gunners resting, soon after their withdrawal from the Vevi area
The New Zealand battalion withdrew, crossing the Pineios river; by dusk, they had reached the western exit of the Pineios Gorge, suffering only light casualties.
Macky was informed that it was "essential to deny the gorge to the enemy until 19 April even if it meant extinction". He sank a crossing barge at the western end of the gorge once all his men were across and set up defences. The 21st Battalion was reinforced by the Australian 2/2nd Battalion and later by the 2/3rd. This force became known as "Allen force" after Brigadier "Tubby" Allen. The 2/5th and 2/11th battalions moved to the Elatia area south-west of the gorge and were ordered to hold the western exit possibly for three or four days.
On 16 April, Wilson met Papagos at Lamia and informed him of his decision to withdraw to Thermopylae. Lieutenant-General Thomas Blamey divided responsibility between generals Mackay and Freyberg during the leapfrogging move to Thermopylae. Mackay's force was assigned the flanks of the New Zealand Division as far south as an east-west line through Larissa and to oversee the withdrawal through Domokos to Thermopylae of the Savige and Zarkos Forces and finally of Lee Force; Brigadier Harold Charrington's 1st Armoured Brigade was to cover the withdrawal of Savige Force to Larissa and thereafter the withdrawal of the 6th Division under whose command it would come; overseeing the withdrawal of Allen Force which was to move along the same route as the New Zealand Division. The British Empire forces remained under attack throughout the withdrawal.
On the morning of 18 April, the Battle of Tempe Gorge, the struggle for the Pineios Gorge, was over when German armoured infantry crossed the river on floats and 6th Mountain Division troops worked their way around the New Zealand battalion, which was subsequently dispersed. On 19 April, the first XVIII Mountain Corps troops entered Larissa and took possession of the airfield, where the British had left their supply dump intact. The seizure of ten truckloads of rations and fuel enabled the spearhead units to continue without ceasing. The port of Volos, at which the British had re-embarked numerous units during the prior few days, fell on 21 April; there, the Germans captured large quantities of valuable diesel and crude oil.
As the invading Germans advanced deep into Greek territory, the Epirus Army Section of the Greek army operating in Albania was reluctant to retreat. However, by the middle of March, especially after the Tepelene offensive, the Greek army had suffered, according to British estimates, 5,000 casualties.The Italian offensive revealed a "chronic shortage of arms and equipment." The Greeks were fast approaching the end of their logistical tether.
General Wilson described this unwillingness to retreat as "the fetishistic doctrine that not a yard of ground should be yielded to the Italians." Churchill also criticized the Greek Army commanders for ignoring British advice to abandon Albania and avoid encirclement. Lieutenant-General George Stumme's Fortieth Corps captured the Florina-Vevi Pass on 11 April, but unseasonal snowy weather then halted his advance. On 12 April, he resumed the advance, but spent the whole day fighting Brigadier Charrington's 1st Armoured Brigade at Proastion. It was not until 13 April that the first Greek elements began to withdraw toward the Pindus mountains. The Allies' retreat to Thermopylae uncovered a route across the Pindus mountains by which the Germans might flank the Hellenic army in a rearguard action.
An elite SS formation - the Leibstandarte SS Adolf Hitler brigade - was assigned the mission of cutting off the Greek Epirus Army's line of retreat from Albania by driving westward to the Metsovon pass and from there to Ioannina. On 13 April, attack aircraft from 21, 23 and 33 Squadrons from the Hellenic Air Force (RHAF), attacked Italian positions in Albania. That same day, heavy fighting took place at Kleisoura pass, where the Greek 20th Division covering the Greek withdrawal, fought in a determined manner, delaying Stumme's advance practically a whole day. The withdrawal extended across the entire Albanian front, with the Italians in hesitant pursuit. On 15 April, Regia Aeronautic fighters attacked the (RHAF) base at Paramythia, 30 miles south of Greece's border with Albania, destroying or putting out of action 17 VVKJ aircraft that had recently arrived from Yugoslavia.
General Papagos rushed Greek units to the Metsovon pass where the Germans were expected to attack. On 14 April a pitched battle between several Greek units and the LSSAH brigade - which had by then reached Grevena - erupted. The Greek 13th and Cavalry Divisions lacked the equipment necessary to fight against an armoured unit but nevertheless fought on till the next day, when the defenders were finally encircled and overwhelmed. On 18 April, General Wilson in a meeting with Papagos, informed him that the British and Commonwealth forces at Thermopylai would carry on fighting till the first week of May, providing that Greek forces from Albania could redeploy and cover the left flank. On 21 April, the Germans advanced further and captured Ioannina, the final supply route of the Greek Epirus Army. Allied newspapers dubbed the Hellenic army's fate a modern day Greek tragedy. Historian and former war-correspondent Christopher Buckley - when describing the fate of the Hellenic - armystated that "one experience[d] a genuine Aristotelian catharsis, an awe-inspiring sense of the futility of all human effort and all human courage."
On 20 April, the commander of Greek forces in Albania—General Georgios Tsolakoglou—accepted the hopelessness of the situation and offered to surrender his army, which then consisted of fourteen divisions. Generals Ioannis Pitsikas and Georgios Bakos had already warned General Papagos on 14 April that morale in the Epirus Army was wearing thin, and regrettably combat stress and exhaustion had resulted in officers taking the decision to put deserters before firing squads. Nevertheless, Papagos condemned Tsolakoglou for his decision to not continue fighting. General Blamey also criticized at the time, Tsolakoglou's decision to surrender without permission from General Papagos.
Historian John Keegan writes that Tsolakoglou "was so determined... to deny the Italians the satisfaction of a victory they had not earned that... he opened quite unauthorised parley with the commander of the German SS division opposite him, Sepp Dietrich, to arrange a surrender to the Germans alone."
On strict orders from Hitler, negotiations were kept secret from the Italians and the surrender was accepted. Outraged by this decision, Mussolini ordered counter-attacks against the Greek forces, which were repulsed, but at some cost to the defenders. The Germans Air Force intervened in the renewed fighting, and Ioannina was practically destroyed by Stukas. It took a personal representation from Mussolini to Hitler to organize Italian participation in the armistice that was concluded on 23 April. Greek soldiers were not rounded up as prisoners of war and were allowed instead to go home after the demobilisation of their units, while their officers were permitted to retain their side arms.