'Harling' was an Allied special operations raid to destroy the Gorgopotamos railway bridge near Thermopylai in Axis-occupied Greece (25/26 November 1942).

The operation was planned from a time late in the summer of 1942 as a means of slowing if not halting the movement of Axis supplies through Greece to the ports from which they would be shipped to the German and Italian forces fighting the British in North Africa, and the plan devised by the Cairo office of the Special Operations Executive was based on the despatch of a team to cut the railway line connecting Thessaloníki and Athens.

Selected as the optimum targets were the Gorgopotamos, Asopos and Papadia viaducts in the area of Brallos. The destruction of the Asopos viaduct was seen as offering the greatest advantage to the Allies as its reconstruction would take longer than those of the other two structures, but the choice was left to the mission’s commander, Lieutenant Colonel E. C. W. Myers.

Once the mission had been completed, the British team was to be evacuated, leaving only Major C. M. Woodhouse, the mission’s second in command, together with the Greek 2^nd Lieutenant Themis Marinos and two radio operators to establish links with the Greek resistance movement.

The first Greek attempts at armed resistance in Macedonia had been destroyed during the summer of 1941 by the Germans and Bulgarians but then, in the course of the spring and summer of 1942, there emerged the first armed guerrilla units in the interior mountain regions of central Greece and Epiros. Right from the start the largest of these was the Greek People’s Liberation Army (ELAS) established by the communist-led National Liberation Front (EAM) and headed by Aris Velouchiotis. The second largest was the National Republican Greek League (EDES) headed by Colonel Napoleon Zervas. The British were largely ignorant of the real nature of the resistance movement in both its military and political aspects.

The SOE party for 'Harling' totalled 12 men divided into three groups each comprising the leader, interpreter, sapper and radio operator: the first group comprised Myers, Captain Denys Hamson as interpreter, Captain Tom Barnes as sapper and Sergeant Len Wilmot as wireless operator; the second group comprised Woodhouse, 2^nd Lieutenant Themis Marinos, Lieutenant Inder Gill, and Sergeant Doug Phillips; the third group comprised Major John Cook, Captain Nat Barker, Captain Arthur Edmonds and Sergeant Mike Chittis. Each group was delivered by a Consolidated Liberator aeroplane.

The first attempt to drop the party into Greece on 28 September failed as the pre-arranged signal fires had not been lit, but the second attempt on 30 September was successful as the pilots located the signal fires and dropped the party near Mt Giona in central Greece. The third Liberator could not spot the signal fires, and Cook’s group jumped near Kaprenissi, which had a strong Italian garrison: one member of the group landed in the town, where he was hidden by the locals. Evading the Italian troops searching for them, the British made for the hills, where they were found by the resistance fighters of Aris Velouchiotis.

Meanwhile the men of the main group were being hidden by the local Greeks and moved constantly to avoid detection by the Italians. Woodhouse set out to Amfissa to establish contact with Cairo. During this time Myers and Hamson, led by a Greek guide, undertook a reconnaissance of the prospective targets. They opted for Gorgopotamos as this seemed to offer the greatest chance of success: its garrison of 80 Italians was small enough to handle, and its location offered good access, cover and line of retreat.

On 2 November, Woodhouse set out to establish contact with Zervas' fighters in the region of the Valtos mountains, and on 14 November Cook’s group rejoined the main party with the news that it had made contact with Velouchiotis. Woodhouse returned on the same day with Zervas and 45 of his men. Zervas was enthusiastic about the operation right from the start, but Velouchiotis was less supportive as the Athens-based leadership of EAM-ELAS still did not appreciate the importance of rural rather than urban resistance to the Axis occupation. In the end, and on his own initiative and contrary to the instructions received from EAM, Velouchiotis decided to participate in the operation.

The force which was thus made available for the operation numbered 150 men: the 12 men of the British party which would constitute the demolition party, 86 ELAS men and 52 EDES men, who would provide cover and neutralise the garrison. The attack was planned to take place at 23.00 on 25 November. Two teams of eight resistance fighters were to cut the rail and telephone lines in both directions, as well as cover the approaches to the bridge itself, while the main force of 100 guerrillas was to neutralise the garrison. The demolition party, divided into three teams, would wait upriver until the garrison had been subdued, and then lay its charges.

The attack on the garrison outposts at the ends of the bridge began as scheduled, but lasted longer than had been expected, and Myers decided to commit the demolition teams while the fighting was still under way. However, the setting of the charges was also delayed as the girders to be destroyed were of a shape different to that which had been expected, and the sappers had to cut the plastic explosive charges to pieces and then reassemble them into the required shapes.

The first charge detonated at 01.30, severely damaging the central pier and collapsing two of the bridge’s spans. The demolition teams then attached new charges to the second pier and the remaining span, and these detonated at 02.21.

In the meantime, the outposts of the resistance fighters had engaged and halted a train carrying Italian reinforcements to the scene. By 04.30 the whole attacking force, which had suffered only four wounded, had successfully disengaged and retreated to its assembly area.

This mission was a major success for the SOE. Although its original purely military objective, the disruption of the supply chain to North Africa, had been rendered superfluous by the Allied victory in the 2^nd Battle of El Alamein, the mission nonetheless revealed the possibilities of major guerrilla actions in serving Allied strategic objectives, encouraged the SOE to aid the development of resistance movements, and provided a major morale boost for occupied Greece.

The 'Harling' party was not withdrawn, as originally envisaged, but was instead ordered to remain in Greece and form the British military mission to Greece. 'Harling' was also, and unfortunately, the last time in which ELAS and EDES co-operated militarily, for within a month there took place the first clashes between the two group’s fighters, which presaged the open conflict that would erupt between ELAS and the other resistance groups in 1943 as the first steps in the Greek Civil War.