Kraft Eberhardt was posted as Staffelkapitän to 8./JG 134 on 4 January 1936 and he remained there until 31 July 1936.

The Spanish Civil War started on 17 July 1936.

After a meeting on 25 July, Adolf Hitler authorised German help to the Nationalist cause under the codename Untemehmen Feuerzauber (Operation Magic Fire).
As part of this, a fleet of Ju 52/3ms under the command of Generalleutnant Helmuth Wilberg was to take General Franco’s forces from Tetuán in Spanish Morocco to Seville. Wilberg was to establish a new, highly covert “Special Staff” to be known as Sonderstab W after its leader.
The initial German help to the Nationalists were in the form of military technicians, 20 pieces of artillery, ammunition, 20 Ju 52/3ms and six Heinkel He 51s (which received the type identification number ‘2’).
On 27 July, the pilots of the Luftwaffe's fighter units, the He 51-equipped I./JG 132 ”Richthofen” at Döberitz and the Ar 65- and Ar 68-equipped I./JG 134 ”Horst Wessel” at Dortmund, received an appeal for ‘volunteers’ to join a mysterious expeditionary force destined for an unidentified foreign country. In some cases, however, word seems to have got out, as in the case of Oberleutnant Hannes Trautloft. Trautloft was actually serving with 9. Staffel of II./JG 134, which had located to Köln-Butzweilerhof following the occupation of the Rhineland. Initial pilots were Oberleutnant Hannes Trautloft of 9. Staffel of II./JG 134, Oberleutnant Herwig Knüppel and Leutnant Wolf-Heinrich von Houwald, both also from III./JG 134, and Oberleutnant Eberhardt, Leutnant Gerhard Klein and Leutnant Ekkehard Hefter. During a farewell inspection along with the rest of the group by General Erhard Milch and Generalleutnant Wilberg, they were told not to enter combat under any circumstances at their eventual destination - the role of the Heinkel pilots would be purely to protect and defend the Junkers transports that would be ferrying troops.
At the Petersen Dock in Hamburg, the pilots and other personnel of the volunteer group boarded the Woerman Line cargo vessel SS Usaramo, onto which they assisted with the loading of 773 crates of equipment. According to Trautloft, ”I would quickly learn that our aircraft were stowed in disassembled components”.
Around midnight on 31 July, the Usaramo sailed from Hamburg bound for Cádiz, in southern Spain.

SS Usaramo with the first contingent of German volunteers arrived at the roadstead off Cádiz on 6 August before docking the next day. They were sent by train to Seville. Hannes Trautloft recalled:

“The next morning we found ourselves at Seville airfield [Tablada], a frequent target for “Red” airmen. On 9 August we started the job of rebuilding our six He 51s - a real piece of teamwork involving pilots and ground personnel. The Spanish personnel were quite surprised to witness us work with such energy, but we really were getting quite impatient and wanted to get our machines into the air as soon as possible.”

“Our single-seaters had to be put together rapidly, as we wanted to strike out as soon as possible to the Front. Breaking open crates, raising aircraft fuselages, attaching wings, fixing bracing struts - that was our first occupation. In doing so, we established friendships with the Spanish pilots [Joaquín García] Morato, [Julio] Salvador, [Luis] Rambaud and others, and with the Spanish mechanics. Many beads of sweat flowed.”

“After some seven days of strenuous work, with our toothbrushes and shaving gear stashed in the stowage compartment of our He 51s, we flew via Salamanca and the Sierra de Gredos to our small combat airfield of Escalona del Prado, near Segovia.
There, on the northern perimeter of the Guadarrama hills, we were located together with an Escuadrilla de reconocimiento, with whom we soon established a warm friendship. The aircraft stood in the open, replacement parts, ammunition and fuel and oil laying protected from the sun under tarpaulins at the edge of the forest. We ourselves likewise lay to some extent protected from the full glare of the sun and slept when we were not flying, or else had language tuition with the Spanish crews.”

“We arrived at Salamanca, the second stopping place on our way to Escalona - a small town close to the Madrid Front. Salamanca was the first combat airfield I saw. We took a big chance in actually finding it because everything, including the aircraft, was very well camouflaged. We refuelled and took off for Escalona, an airfield that we heard was incredibly small and hard to find. It lay so close to the front that it was quite probable that we would engage the enemy. Nevertheless, we found it after half-an-hour and landed. The airfield was so poor that we were worried whether our Spanish comrades would be able to fly our aircraft from there.
Next day I had a most annoying experience. Full of enthusiasm and idealism, five Spaniards proudly climbed into our aircraft. They did not want foreigners to fight for them while they had to stay on the ground with nothing to do. But as they returned, my aircraft crashed on landing. Fortunately, the other Heinkels managed to land safely. From now on, without an aircraft, I had to stay on the ground while the others each shot down two or three enemy in short order. I had nothing better to do than to wait for new aircraft to come from home. I kept thinking that they would arrive too late because the “Rojos” would be forced to surrender in front of Franco’s massive offensive.”

Of the time at Escalona del Prado, Oberleutnant Herwig Knüppel wrote:

“A fighter pilot must always be ready for action. We flew other pilots back in a Ju 52 in rotation in order to fetch aviation fuel for our next flights over the front. Our mechanics worked untiringly to maintain the engines and machine guns. We – as the “Kette Eberhardt” – flew four to five times daily to the front, with a view of the buildings of Madrid lying in the distance in the haze of the sun. Eberhardt, Trautloft and I proudly called ourselves “the Jäger from Guadarrama”.”

On the afternoon on 25 August, the German fighters made their operational debut in support of the drive on Madrid. A patrol comprising Oberleutnant Eberhardt (now in nominal command of the German fighter force) , Oberleutnant Hannes Trautloft and Oberleutnant Herwig Knüppel took off. The Spanish heat made conditions somewhat unusual for aerial combat, and as Trautloft recorded ’I sat in my aircraft in shorts and a T-shirt - my tennis clothes!’ Knüppel recalled:

“It was once again a sunny day with a clear blue sky. Catalonia lay beneath us, with its superb Guadarrama forested hills, on whose heights battles were being fought on the Puerto de Somosierra, Navicicerada and on the pass road from León. In the northwest, beyond the hills, lay Segovia, and in the southwest, the mighty rectangle of the Escorial, with its imposing walls, domes and towers, while in the south, in the haze of the summer day, Madrid. We were flying on our way to the west. Suddenly, Oberleutnant Eberhardt gave the signal for attack.”

“As I approach I see the gunner aiming his gun at me and then the muzzle lights up as he opens fire. It all looks rather harmless. With my first burst, the gunner disappears - his machine gun points vertically towards the sky. The “Red” now pushes over into a steep dive. My second burst is brief, but on target, because all of a sudden the Breguet rears up, rolls over, roars towards the earth in a steep, uncontrolled dive and smashes into the ground north of the village of Comenar.”

During a mission to Madrid on 26 August, Oberleutnant Eberhardt and Oberleutnant Herwig Knüppel claimed a Breguet XIX each. Knüppel recalled:

“Now, full power and attack! I head for one of the enemy Aufklärer, a Breguet 19. I have him in my cross-wires and open fire. He dives away beneath me. I make yet another attack – l his engine stops and his observer stops firing. He crashes close behind the enemy line. In my great joy over this aerial victory, I perform a loop. But already an enemy fighter, a French parasol monoplane, is sitting on my tail. Just as I was about to turn onto him, he shot upwards. I was unfortunately unable to catch him, as his aircraft climbed better and was faster.”

On 29 August, Oberleutnant Eberhardt claimed an unconfirmed Potez 540 over the Sierra Guadarrama.
It seems that Oberleutnant Herwig Knüppel and Oberleutnant Hannes Trautloft were involved in (inconclusive) combat with Potez 540s over the Sierra Guadarrama during the day and they reported that during their first pass, they had their windscreens smeared with oil from the shot-up Potez, forcing them to break off their attacks. They were also set upon by a Dewoitine D.372 fighter.

On 30 August, the three He 51Bs flown by Oberleutnants Eberhardt, Herwig Knüppel and Hannes Trautloft chased three Potez 540 deep over enemy territory, Trautloft angrily expended almost all of his ammunition from just 50 metres away and behind. In response, the bomber simply went into a steep glide, again spraying oil all over the German’s windscreen and severely limiting his ability to see anything. Eberhardt and Knüppel were similarly frustrated. Lessons were being learned, for as Trautloft noted:

“From this range we can't possibly have missed. We suspect that the pilot’s seat in the Potez bomber is armoured. Therefore in future we shall have to attack from the front.
“I attempt an attack from the front in an effort to knock out the pilot. But he has, meanwhile, got a good lead and my machine just is not fast enough. In addition we are almost out of ammunition, so there is nothing else for it but to break off our attack.”

On a later mission the same day Oberleutnant Hannes Trautloft (again flying in his tennis gear) was bounced by an enemy fighter (probably a Dewoitine D.371) whose machine gun fire raked the right wing of his Heinkel (2-4), sending it into a spiral dive. With his controls shot away, Trautloft decided to parachute, and opened his parachute at about 8000 ft. The attacking Republican fighter attempted to return for a second pass and open fire at the vulnerable German airman, but Eberhardt and Herwig Knüppel chased him away. Trautloft recalled:

“In spite of these encouraging results against the Potez, it was clear that our aircraft were not superior enough for us to feel completely safe from the enemy. In fact, on 30 August, I was, for my part, shot down and had to bail out. I was lucky that I was not wounded and that I landed behind Nationalist lines. However, Franco’s troops were, of course, not only surprised to see a tennis player landing in their positions by parachute, they were also very suspicious of me. I did not speak Spanish very well and I suppose they thought that I could have been a foreign volunteer for the “Red Army”. I proved to them that this was not the case by showing them my passport. In it was written “Este aparate y su piloti Don. Hannes Trautloft, estan al servicio del Ejercito Nacional del Norte”. After having carefully read these lines, the Spanish officer shook my hand and I was treated in a very friendly fashion.'

On 6 September, Oberleutnants Eberhardt and Herwig Knüppel claimed a Potez 540 each.

On 23 September, the German Jagdstaffel was ordered briefly to Ávila in the first of what would become many temporary relocations to support the Nationalist ground offensives. They were then quickly relocated north to the Basque town of Vitoria, on the Bilbao front, where the Republicans continued to hold ground on the coast.
On 29 September, they were ordered back to Ávila.

Taking off from Ávila on 30 September, Oberleutnant Hannes Trautloft managed to inflict sufficient damage on a Potez 540 that it crashed into the ground. Staffelkapitän Oberleutnant Eberhardt claimed a second Potez.

By the beginning of October 1936 six of the new batch of He 51s had arrived in Spain, together with ten volunteer pilots and more mechanics - ”a necessary and welcome strengthening”, as Oberleutnant Herwig Knüppel described it. ”Just like we had done two months previously, they had put together their He 51 single-seaters in Seville, for which we soon almost fell around their necks with joy.”
This latest batch of pilots comprised Oberleutnante Dietrich von Bothmer, Oskar Henrici and Günther Radusch, Leutnante Kurt von Gilsa, Paul Rehahn and Henning Strümpell and Unteroffiziere Willi Gödecke, Kowalski, Ernst Mratzek and Erwin Sawallisch. It was now possible to split the Jagdstaffel into two elements – five aircraft under Oberleutnant Hannes Trautloft headed north on 5 October to León to escort supply and bombing missions around the Nationalist enclave at Oviedo in Asturias, while the others, under Oberleutnant Eberhardt, went to Barahona and eventually on to Zaragoza. Communications between the two Ketten would be maintained by a solitary Fokker F VII that had been assigned to the Staffel.

By the middle of October, more Heinkels had arrived, and the strength of the fighter Staffel increased to 14 He 51s.

In the afternoon on 13 November 1936, nine He 51s from the German Legion Condor took off from Ávila to provide escort for five German-flown Ju 52/3ms and three He 46s, which were to attack the Republican positions on the west bank of the Manzanares. It seems that at least six CR.32s also were present.
At 15:00, twelve I-16 type 5 “Moscas” and twelve I-15s intercepted them over Madrid. The I-16s were led by the Russian squadron leader Kapitan Sergey Tarkhov (’Antonio’) (he was the commander of the first and newly created escuadrilla of I-16s) in their first combat while the I-15s (Escuadrilla Palancar) were again led by Starshii Leitenant Pavel Rychagov. All Republican pilots taking part in this combat were Russians.
The Republican fighters dove on the Henrici Kette. Unteroffizier Ernst Mratzek was able to claim an I-16 as it dove past. Oberleutnant Oskar Henrici claimed a Russian fighter in the same way as the He 51s dove into the clouds. A bitter dogfight raged over Madrid at 1,500 meters. The Knüppel Kette dove into a cloud, reversed course in a steep turn and re-emerged below the Republican aircraft. Oberleutnant Herwig Knüppel and Unteroffizier Erwin Sawallisch claimed two I-15s; Sawallisch made his way home with some difficulty with shot-up tail surfaces. The Eberhardt Kette had remained above the bombers as top cover. Oberleutnant Eberhardt collided with an enemy fighter he had shot down and was killed when his fighter crashed to the ground at Casa de Campo; the Russian pilot was able to bail out. Oberleutnant Henrici took a bullet through the lung, but was able to land his aircraft in friendly territory at Alcorcon. As he left his aircraft, however, he collapsed and died. The German Staffel became completely scattered, each pilot seeking cover in cloud and making his own way back to Avila. Leutnant Henning Strümpell and Leutnant Dietrich von Bothmer reported the destruction of two further I-15s.
Henrici was probably shot down by Leitenant Sergey Chernykh, (I-16 in Escuadrilla Kolesnikov). It seems that Eberhardt collided with Tarkhov since it’s reported that he single-handed fought against a number of He 51s before being forced to bail out after a collision. While hanging in his parachute, Republican soldiers mistook him for Nationalist pilot and opened fire, hitting him six times. Tarkhov landed in Madrid but was attacked by the public because they thought he was a German. He died of his injuries at Gómes Ulla hospital on 23 November. This led General Miaja to the issue following order the next day:

“Any aviator who jumps from his aircraft using a parachute is out of the battle and, therefore, I order all forces defending Madrid not to shoot at parachutists under any circumstances. They may be our own men, but, if they prove to be enemies they can provide us with valuable information, which will be of great use for our operations.”

“13 November 1936 was the blackest day for the Jagdstaffel Eberhardt. We flew in the afternoon as escort for the Kampfstaffel of Oberleutnant von Moreau, starting out from Ávila and heading to Madrid. Following the second bombing run, we were attacked by around 24 low-winged and biplane fighters (Ratas and “Curtisses”) from above on the eastern border of Madrid at an altitude of between 1200-1500 metres. It developed into an exceedingly hard air battle.”

“On Friday, 13 November 1936, we encountered the Ratas for the first time and a wild melee resulted. We downed five of them, but what were these victories when compared with the loss of our Staffelführer? This only served to show that our good old He 51s were too slow compared with the new Ratas - they could play with us as they wanted. Furthermore, the Soviet “Martin Bombers” [Tupolev SB], which were arriving daily, were 50 km/h faster than us, and the people were scared of them. Feverishly, we waited for the Bf 109s to arrive from Germany.”

At the time of his death, Eberhardt was credited with 5 biplane victories.
He was decorated with the Spanienkreuz in Gold mit Schwerten for his service in Spain.

On 6 June 1939, several of the German veterans that served in Spain was decorated with the Spanienkreuz in Gold mit Brillanten for their service in Spain. This included Eberhardt (posthumous), Harro Harder, Eduard Neumann and Oskar Henrici (posthumous)

Claims:

Kill no.	Date	Time	Number	Type	Result	Plane type	Serial no.	Locality	Unit
	1936
1	25/08/36	p.m.	1	Breguet XIX	Destroyed	Heinkel He 51B		Madrid area	J/88
2	26/08/36		1	Breguet XIX	Destroyed	Heinkel He 51B		Madrid area	J/88
	29/08/36		1	Potez 540	Unconfirmed	Heinkel He 51B		Sierra Guadarrama	J/88
3	30/08/36		1	Potez 540	Destroyed	Heinkel He 51B		Sierra Guadarrama	J/88
4	06/09/36		1	Potez 540	Destroyed	Heinkel He 51B		Spain	J/88
5	30/09/36		1	Potez 540	Destroyed	Heinkel He 51B		Ávila area	J/88
	13/11/36	15:00-	1	I-16 (a)	Unconfirmed	Heinkel He 51B		Madrid area	J/88

Biplane victories: 5 destroyed, 2 unconfirmed.
TOTAL: 5 destroyed, 2 unconfirmed.
(a) The Soviet volunteers claimed 4 He 51s while losing 4 I-16s and pilots. The German pilots claimed 2 I-16s and 5 I-15s (1 of each as an unconfirmed) while losing 2 He 51s.

Sources:
Aces of the Legion Condor – Robert Forsyth, 2011 Osprey Publishing, Oxford, ISBN 978-1-84908-347-8
Aces of the Luftwaffe
Aircrew Remembered
Luftwaffe Officer Career Summaries – Henry L. deZeng IV and Douglas G. Stankey
Russian Fighter Aces of 1914-1953 years
Soviet airmen in the Spanish civil war 1936-1939 - Paul Whelan, 2014 Schiffer Publishing Ltd, ISBN 978-0-7643-0
Spanish Republican Aces – Rafael A. Permuy López, 2012 Osprey Publishing, Oxford, ISBN 978-1-84908-668-4
The Legion Condor - Karl Ries and Hans Ring, 1992 Schiffer Publishing, ISBN 0-88740-339-5
The Luftwaffe, 1933-45
Additional information kindly provided by Alfredo Logoluso.