'Amsterdam' (ii) was a US air operation, using Boeing B-17 Flying Fortress four-engined aircraft of the USAAF, to deliver weapons, other equipment and agents of the Office of Strategic Services to the Slovak forces concentrated in the area of Tri Duby airfield during the Slovak national rising (7 October 1944).

The rising was organised by the Slovak communist resistance movement, and launched on 29 August 1944 from Banská Bystrica in an attempt to oust the collaborationist government of Jozef Tiso. Although the rebel forces were defeated by Germany, guerrilla warfare continued until the occupation of Slovakia by the Soviet forces in 1945.

Elements of several ethnic and political groups were involved in the rising, these including large rebel units of the Slovak army, Slovak partisans, communist partisans and international forces, and given this fact the rising did not have unified popular support within Slovakia.

Edvard Benes, leader of the Czechoslovak government-in-exile in London, had spurred preparations of a possible rising in 1943 when he made first contacts with dissident elements within the army of collaborationist Slovakia, and in December of the same year several groups (the government-in-exile, Czechoslovak democrats and communists, and Slovak army elements) created the clandestine Slovak National Council and signed the so-called Christmas Treaty as a joint declaration to recognise Benes’s authority and to recreate Czechoslovakia after the war. This council was responsible for in-country preparations, which were supervised from March 1944 by a Slovak army officer, Podplukovnik Ján Golian. The conspirators gathered money and stockpiled ammunition and other supplies at military bases in the central and eastern part of Slovakia for the rebel forces, who designated themselves as the Czechoslovak Forces of the Interior and as the 1^st Czechoslovak Army. Moreover, about 3,200 Slovak soldiers deserted and joined partisan groups or the Soviet forces.

During the summer of 1944 the partisan movement intensified its war against the German occupation forces, primarily in the mountains of north central Slovakia. In this period the Soviet forces began to advance toward Slovakia in July and, by August, were at Krosno in Poland, and therefore within 25 miles (40 km) of the north-eastern part of the Slovak frontier. This paved the way for sympathetic senior officers to relocated two divisions of the Slovak army, together with the entire eastern portion of the Slovak air force, to north-east Slovakia for the execution of one of the two planned options to begin the rising.

These options were, firstly, that the two divisions would seize control of the Dukla Pass, connecting Poland and Slovakia through the Carpathian mountains, in a move co-ordinated with the arrival of Marshal Sovetskogo Soyuza Ivan D. Konev’s 1^st Ukrainian Front or, secondly, respond to Golian’s orders to start the rising by preventing the German forces from taking control of the pass and so buy the time needed for the Soviet forces to arrive and debouch into Slovakia through this strategic feature.

The chief-of-staff for the two divisions was Plukovnik Viliam Talský, who had agreed in advance with the army leadership and the planning committee of the Slovak National Council to execute either of these two plans depending on the circumstances he faced.

On 27 August a group of communist partisans under Soviet command in Kiev killed 30 members of a German military mission in Martin as they were en route from Romania, which had just changed sides to support the Allies. German troops began to occupy Slovakia on the following day as a first step in quelling what Germany saw as a rebellion.

At 19.00 on 29 August the Slovak defence minister, General Ferdinand Čatlos, announced on state radio that Germany had occupied Slovakia, and one hour later Golian sent the coded message to all units to begin the rising. Instead of adhering to the agreed plan, Talský gathered the entire eastern element of the Slovak air force on 30 August and abandoned the two army divisions when he flew to a prearranged landing zone in Poland to join the Soviet forces.

The two divisions, left in chaos and without senior leadership, were quickly disarmed during the afternoon of 30 August before a single shot had been fired. The rising had therefore got off to a premature and ineffectual start, and thereby lost a crucial component of its overall plan as well as its two best equipped divisions, the only formations that might possibly have resisted the German advance.

Accounts of the number of Slovak combatants vary very considerably. At first, the rising’s forces comprised some 18,000 soldiers, a total increased to 47,000 after mobilisation on 9 September and later to 60,000, plus 18,000 partisans from more than 30 countries. The Slovak insurgent air force had a small number of aircraft, most of them obsolete. In addition to Slovak national forces, the combatants included elements of various other groups ranging from escaped French prisoners of war to Soviet partisans and operatives of the British Special Operations Executive and US Office of Strategic Services.

In the air the Slovak insurgents had to rely primarily on biplane aircraft of very limited tactical capability, and on the ground made use of improvised armoured trains to fight against the better equipped German forces.

In addition to Soviet aid, the insurgents received in 'Amsterdam' (ii) limited quantities of matériel delivered by B-17 bombers.

The rising started at 08.00 on 29 August under Golian’s command. During the morning of the following day, insurgent forces entered Banská Bystrica and here established their headquarters. German troops disarmed the Slovak army in the eastern part of the country on 31 August: many of the soldiers were sent to camps in Germany, but significant numbers managed to escape the German net to join the Soviet-controlled partisans or merely to return home. On 5 September Golian became the commander of all the rebel forces in Slovakia and was promoted to general.

The Slovak forces in central Slovakia mobilised 47,000 men, and Golian’s first analysis of the situation predicted that he had the strength to resist the Germans for about two weeks. By 10 September the insurgents had gained control of large areas of central and eastern Slovakia. The areas included two airfields, and this made it possible for the Soviets to fly in equipment.

Tiso’s pro-German government remained in power in Bratislava, and Germany deployed 40,000 Waffen-SS troops under SS-Obergruppenführer und General der Waffen-SS Gottlob Berger to suppress the uprising. It was these SS forces which detained and disarmed the two Slovak divisions, whose 20,000 men were to have secured the mountain passes to help the Soviet forces to advance into Slovakia.

Benes had met with Iosif Stalin and Vyacheslav Molotov, respectively the Soviet premier and foreign minister, in Moscow during December 1943 to secure Soviet support for the rising. Stalin and the Stavka failed to deliver the needed support in time to be of practical aid to the insurgent army, and even blocked offers of military aid from the Western Allies, as they had only a few weeks earlier during the Polish national rising.

Meanwhile, Konev and the Soviet partisan headquarters in Kiev continued to undermine the efforts of the Slovak insurgent army by ordering partisan groups operating in forward positions within Slovakia to conduct their own operations and to avoid co-ordination with the Slovak insurgent army. The Soviet-led partisans even demanded and indeed seized weapons and munitions that had been stored for the insurgent Slovak army, which desperately needed these munitions.

The majority of the weapons air-dropped by the Soviets over insurgent-held territory in eastern and northern Slovakia were quickly seized by the partisans, with the result that only small quantities reached the stronger and better trained Slovak insurgent army.

On 8 September the Soviet forces began an offensive to penetrate the Dukla Pass from Poland into Slovakia and also tried to fight through the Carpathian mountains into Slovakia in a poorly planned undertaking which resulted in heavy casualties on each side. The fighting then bogged down for nearly two months.

Benes, the Soviet partisans and various Slovak factions now began to dispute who should have operational control. Although he tried on several occasions, Golian could not bring the sides together and so create the means to co-ordinate the various Slovak efforts. General Rudolf Viest arrived by air and took command on 7 October with Golian as his second-in-command. After factional rivalries resurfaced in the face of military failure, it was therefore impossible for Viest to take control of the situation. The rising also coincided with the stalling of the Soviet summer offensive, the failure of the Polish national rising, and other troubles on the side of the Western Allies.

The Soviet forces and their Czechoslovak allies failed to effect a rapid penetration through the Dukla Pass despite the fierce fighting between 8 September and 28 October, in the process suffering some 85,000 casualties including 21,000 dead. The Czechoslovak government-in-exile failed to convince the Western Allies to ignore Stalin’s obstruction and send more supplies to the area.

After the start of the uprising, the Czechoslovak government-in-exile argued for the commitment of of Czechoslovak units deployed on the Eastern Front with the Soviets, and the two such elements which did arrive were the 1^st Czechoslovak Independent Fighter Regiment, which arrived at Zolná airfield near Zvolen on 15/17 September with 21 Lavochkin La-5 single-engined fighters, and the 2^nd Czechoslovak Parachute Brigade, which was transferred from the Carpathians between 25 September and 15 October.

On 17 September two B-17 machines delivered an OSS mission headed by Lieutenant James Holt-Green, and on the following day there arrived the SOE team of Major John Sehmer on its way to Hungary. The reports of these two Allied teams confirmed the suspicions of Western Allies that the outcome of the rising was becoming increasingly parlous.

On 19 September Berger was succeeded by General Hermann Höffle in command of a German strength which had, by this time, risen to 48,000 men in eight (including four Waffen-SS) divisions and one pro-Nazi Slovak formation. On 1 October the insurgent forces were renamed the 1^st Czechoslovak Army in Slovakia, in order to symbolise the beginning of a Czech and Slovak reunification that would be recognised by the Allied powers.

On 7 October, 'Amsterdam' (ii) saw the arrival at Tri Duby of B-17 bombers, escorted by North American P-51 Mustang long-range fighters, to deliver supplies and OSS agents. The aircraft also collected 15 Allied pilots whose aircraft had been shot down over Slovakia during past few month and also five French partisans.

A major German counter-offensive began on 17/18 October when 35,000 German troops entered the country from Hungary, which had been under German military occupation since 19 March 1944. Stalin immediately ordered Marshal Sovetskogo Soyuza Rodion Ya. Malinovsky’s to switch the axis of his 2^nd Ukrainian Front from eastern Slovakia to Budapest, the capital of Hungary. The westward advance of the Soviet forces slowed to a halt late in October as Stalin’s interests focused on Hungary, Austria and Poland rather than Slovakia or the Czech lands. By the end of October the Axis forces, now trimmed to six German divisions and one pro-Nazi Slovak unit, had retaken most of the territory the insurgent forces had earlier liberated, and divided and encircled the Slovak forces in operations which cost each side at least 10,000 casualties.

The insurgent forces were forced to leave Banská Bystrica on 27 October as the German moved against the town, the local SOE and OSS agents retreating into the mountains alongside the thousands of others fleeing the German advance. The rebels were now faced with the need to switch their tactics from those of conventional warfare to those of guerrilla warfare, and on 28 October Viest sent London a message that organised Slovak resistance had come to an end. On 30 October Höffle and Tiso celebrated in Banská Bystrica: Tiso’s involvement was claimed by some to have been an effort to save the lives of captured Slovak soldiers, who were deported to concentration camps, and also to save three Slovak cities from German bombardment.

Partisans and the remnants of the Slovak regular forces continued their efforts in the mountains. In retaliation, German Einsatzgruppen executed many Slovaks suspected of aiding the rebels and destroyed 93 as 'collaborationist'. A later estimate of the death toll was 5,304, in addition to about 10,000 killed and wounded in the campaign, and the authorities discovered 211 mass graves resulting from those atrocities. The largest of these were at Kremnička and Nemecká, where the death tolls were 747 and 900 respectively.

On 3 November the Germans captured Golian and Viest in Pohronský Bukovec, and after interrogating them executed both officers. The various SOE and OSS teams eventually joined forces and sent a message in which they requested immediate assistance, which was impossible. The Germans surrounded and captured both groups on 25 December: some of the men were summarily executed, and the others were sent to Mauthausen concentration camp, where they were tortured and killed.