Ladislao Duarte Espés was born in Erla, Saragossa, on 6 September 1914.

Duarte enrolled in the flying course at the Escuela de Vuelo on 5 January 1937. He logged 16 hours dual elementary instruction and 23 hours solo flying in DH 60s, Farman F.480s and E-34s, followed by 20 hours in Breguet XIXs during his advanced training.

He enlisted in the air force as a pilot sargento in April 1937 and undertook the fighter pilots’ course. His instructor, teniente Emilio Galera Macías, rated him as ‘highly skilled, highly devoted and highly spirited’.
Upon completion of the course Duarte converted onto the I-15 at Madrid and was then posted to the Northern front, where he joined the 3^a Patrulla of the Escuadrilla de Caza del Norte.

In July 1937, capitán Ramón Puparelli Francia was ordered to take his ten I-15s to Santander to reinforce the northern fighter force, which had lost most of their aircraft in frequent air raids on Somorrostro airfield.
Four more I-15s under the command of teniente Juan Comas Borrás joined soon afterwards, so that 45 Chatos were now available for operations on the Northern front. They were reinforced by eight Soviet-flown I-16 Moscas led by Valentin Ukhov, which arrived on 2 July.
Capitán Ramón Puparelli Francia assumed command of both the I-15s and I-16s.
Following teniente José Riverola Grúas’ departure for the Central front, teniente Leopoldo Morquillas Rubio was appointed CO of the Escuadrilla de Chatos del Norte. The Escuadrilla de Chatos del Norte was comprised of the following pilots and aircraft during operations on the Santander front in July 1937:

Unit	Pilot	Aircraft type	Aircraft code
1a Patrulla	Teniente Leopoldo Morquillas Rubio	I-15	’CA-57’
	Teniente Jaime Buyé Berni	I-15	’35’
	Teniente Nicomedes Calvo Aguilar	I-15	’29’
	Sargento Rafael Magriña Vidal	I-15	’13’
2a Patrulla	Teniente Esteban Nazario Ortiz Bueno	I-15	’12’
	Teniente Miguel San José Andrade	I-15	’50’
	Sargento Miguel Galindo Saura	I-15	’28’
	Sargento Andrés Rodríguez Panadero	I-15	’20’
3a Patrulla	Teniente Juan Comas Borrás	I-15	59
	Teniente José González Feo	I-15	’30’
	Sargento Miguel Zambudio Martínez	I-15	’62’
	Sargento Duarte	I-15	’23’
Reserve pilots	Teniente Julián Barbero López
Reserve pilots	Sargento Antonio Rodríguez Jordán
Reserve pilots	Sargento Antonio Miró Vidal
Reserve pilots	Sargento Román Llorente Castro

On 18 August Juan Comas Borrás became a teniente, with fellow pilots Duarte, Miguel Zambudio Martínez and Andrés Rodríguez Panadero also being promoted.

On 22 August, 11 CR.32s from the 32^a Squadriglia clashed with 12 I-15s from Escuadrilla de Caza del Norte during an escort mission over Ontaneda on the Santander front. Italian pilots claimed four destroyed and five probables. Capitano Ernesto Botto claimed two of the I-15s.
Teniente Miguel Galindo Saura, CO of the Republican unit, was injured when he bailed out near Puerto del Escudo and was captured, while squadron mate Angel Martín González died when he crashed trying to force-land his battle-damaged I-15 near Suances.
Teniente Duarte replaced Galindo as CO of the Escuadrilla de Caza del Norte.

On 30 September, Leutnant Erich Woitke of 1.J/88 (Bf 109B) took on eight enemy fighters over Gijón. He claimed an I-16, while Feldwebel Norbert Flegel (2.J/88) claimed an unconfirmed Chato.
It seems that the German fighters had been involved in combat with the fighters from Escuadrilla de Caza del Norte where teniente Duarte (CO) distinguished himself in combat over Gijón with five Bf 109s, the operations record book entry for the day noting:

“At 1330 hrs three biplanes and three monoplanes were scrambled when seven enemy twin-engined aircraft and ten fighters were reported over Gijón. A combat ensued, and one of our monoplane fighters was shot down. It was flown by sargento Daniel Ranz [Daniel Ranz y Diez de Artazcoz], who was killed. His aircraft was a write-off. The bombers attacked the airfields at Carreño and Vega without result. The escuadrilla CO, teniente piloto Duarte, and sargento Castillo engaged five monoplanes and deserve praise for their remarkable feat. Their aircraft landed safely although sargento Castillo’s was severely damaged.”

On 18 October, teniente Duarte, CO of the Escuadrilla de Caza del Norte, led his fighters on patrol over Gijón. The government fighters engaged Bf 109s and He 111s in a battle that lasted 1 hr 20 min. The I-15 of sargento Miguel Castillo Puerta was shot down into the sea near the port, but the aircraft had enough buoyancy to enable the pilot to escape from his cockpit and sit on the tail until he was rescued.
The pilots led by Duarte claimed to have shot down two Bf 109s and a He 111.
This was Duarte’s last combat over the north and he left the front two days later and, travelling via Biarritz and Toulouse, was held in France for several days.

During the campaigns in Santander and Asturias many pilots were killed, wounded or reported missing. The government airmen had to fight under conditions of clear inferiority, mainly due to the lack of strength in depth and also because their airfields were systematically bombed, with heavy losses both in men and materiel. After the Republican defeat on the Asturias front, the Chatos flown by teniente Duarte and sargento Román Llorente Castor, as well as sargento Luis de Frutos González’s Mosca, were the only fighters that managed to escape to France on 20 October 1937.
In total, 43 I-15s and 16 I-16s had been lost during the campaign.

By late November the core of the 4^a Escuadrilla of Grupo N^o 26, commanded by teniente Duarte, had been gathered together from pilots and groundcrew evacuated from the north. This four escuadrillas structure was subsequently maintained by the Grupo N^o 26 for the rest of the war, as plans to create a 5^a Escuadrilla did not materialise.
The 4^a/26 patrolled the Barcelona area until being sent to Sagunto airfield to swap its aircraft for those of the 1^a Escuadrilla de Chatos that had been flown by Soviet pilots. The latter then returned to the USSR.

On 20 February 1938, teniente Duarte (CO 4^a/26), claimed a Bf 109 over Valdesebro. Reportedly the claim was made during the night(!).

Duarte (CO 4^a/26) was promoted to capitán in March 1938.

On 10 March, K/88 made three missions. During the first and taking off from Alfaro at 06:00, the four staffeln joined to attack Candasnos. At about the same time, the Do 17s of A/88 took off from Bunuel and all four staffeln of the Jagdgruppe took off from Sanjuro. At 07:00, the bombers of K/88 arrived over the Republican airfields at Caspe, Sarinena and Candasnos. Conditions were hazy. At Caspe five enemy aircraft were claimed destroyed on the ground. The airfield of Bujaraloz were bombed by the Do 17 Staffel and soon afterwards was forced to endure a low-level strafing attack by several He 111s. Returning from a high-level attack on Candasnos, the Heinkel bombers roared over Bujalaroz with all guns blazing. The He 111 unit set course for home leaving one parked aircraft in flames. It seems that He 111 25-7 from 4.K/88 returned for a second attack when it was attacked from behind and below by an I-15 just as it had crossed the airfield and forced to land at Bujaraloz (20km from Candasnos). The crew of Feldwebel Willi Hesse (pilot), Unteroffizier Theo Kowollik (radio operator), Unteroffizier Karl Hoffmeister (engineer, who reported that he couldn’t fend of the attack due to a jamming gun), Leutnant Kurt Kettner (commander and observer) and Obergefreiter Heinz Clacery (observer and had been invited for the trip) all became PoWs (they were exchanged on 2 Janaury 1939). This was the only He 111 lost during the day.
Flying from Candasnos, the 4^a/26 scrambled nine I-15s at 06:45 to intercept them and claimed two He 111s shot down over the airfield, one of which was credited to capitán Duarte (CO) for his last aerial success of the civil war. Romulo Negrin Mijoilar also took part in this intercept flying in CC-011.
I-16 CM-141 from 1^a/21 was destroyed by fire at Caspe during the day.

He subsequently led the 4^a Escuadrilla during operations in Extremadura, flying from Saceruela airfield in Ciudad Real.

On 23 August the commander of the Escuadra N^o 11, mayor Isidoro Jiménez, recommended capitán Duarte (CO 4^a/26) for the Medalla del Deber (Medal for Duty), commending him for his ”extremely high morale and fighting skills” and for being ”highly admired by his comrades for his determination in combat and great leadership qualities”.

On 6 September the 4^a/26 moved to La Señera airfield, in Valencia.

On 7 September, capitán Duarte (CO 4^a/26) was shot down by anti-aircraft fire while he was making a strafing attack on the Teruel front. His I-15 was set on fire but Duarte managed to bail out behind friendly lines. Although suffering burns, he was rescued by Republican infantrymen and spent the next three months in Valencia's El Vedat hospital.
Capitán Duarte (CO) was replaced as CO by teniente Emilio Ramírez Bravo. By his own account, Duarte’s unit had shot down about 30 enemy aircraft during his time as CO.
Duarte was promoted to mayor shortly after being wounded.

Upon being discharged from hospital, Duarte was sent to Catalonia to take command of the Grupo N^o 26 in the north as Vicente Castillo Monzó had become CO of both escuadrillas in the south.

On 5 February 1939 Duarte was at Figueras, but upon defeat by the Nationalists he crossed the Pyrenees into France, where he was interned until he was able to travel to the Soviet Union.

Duarte ended the Spanish Civil War with 4 biplane victories.
According to Duarte´s own statement, the 4^a Escuadrilla claimed a collective total of 30 aircraft destroyed, which included his own individual score of victories.

He fought with the Red Army Air Force during World War 2, serving in 964 IAP with Antonio Arias Arias.
Details of Duarte´s World War 2 combat record in the USSR remain unknown.

Duarte considered returning to Spain in July 1957 but decided against it for fear that he would be jailed. Still living in the USSR in November 1979, he subsequently died there (date and location unknown).

Claims:

Kill no.	Date	Time	Number	Type	Result	Plane type	Serial no.	Locality	Unit
	1937
1	30/09/37	13:30	1	Bf 109 (a)	Destroyed	I-15		Gijón	Escuadrilla de Caza del Norte
2	30/09/37	13:30	1	He 111	Destroyed	I-15		Gijón	Escuadrilla de Caza del Norte
	1938
3	20/02/38	night	1	Bf 109	Destroyed	I-15		Valdesebro	4a/26
4	10/03/38	06:45-	1	He 111 (b)	Destroyed	I-15		Candasnos airfield	4a/26

Biplane victories: 4 destroyed.
TOTAL: 4 destroyed.
(a) Claimed in combat with Bf 109s from J/88.
(b) Republican fighters claimed 3 He 111s during the day but only 25-7 from 4.K/88 was lost (crew PoW) when it crash-landed at Bujalaroz after having been shot down by an I-15.

Sources:
Aces of the Legion Condor – Robert Forsyth, 2011 Osprey Publishing, Oxford, ISBN 978-1-84908-347-8
Air War over Spain - Jesus Salas Larrazabal, 1974 Ian Allan Ltd, Shepperton, Surrey, ISBN 0-7110-0521-4
Fighter Pilots Of The Spanish Republic (Vol. 1) - Rafael A. Permuy López, Historica 36/39 no. 1, ISBN 84-87314-89-9
Spanish Republican Aces – Rafael A Permuy López, 2012 Osprey Publishing, Oxford, ISBN 978-1-84908-668-4