Alférez Emelio O’Connor Valdivielso was posted to Escuadrilla 4-E-3 of Grupo 3-G-3 in February 1938.

In the end of June 1938, Joaquín García Morato assumed command of the second Fiat group (3-G-3).
Pilots in Escuadrilla 3-E-3 (later 5-E-3) were:
Capitán Javier Murcia Rubio (CO)
Ignacio Alfaro Arregui
G. Queipo de Llano Martí
Andrés Robles Cebrián
Joaquín Chapaprieta Inglada
Alfonso Rubial
García de Juan

Pilots in Escuadrilla 4-E-3 (later 7-E-3) were:
Capitán Heraclio Gautier Larrainzar (CO)
Teniente Joaquín Velasco Fernández Nespral
Teniente O’Connor
Acuña
Fernando Arrechea Belzunce
Enrique Munaiz de Brea
Alférez Alonso Fariña

Pilots in the Escuadrilla 6-E-3 were:
Capitán Jose Barranco del Egido (CO)
Teniente José Larios y Fernández Villavicencio
Muerza
José Andrés Lacour Macia
R. Bartolomé Chávarri
Kindelán
Carracido P. Téllez Rivas

On 1 August, near Fayón, a group of Spanish pilots led by comandante Joaquín García Morato (3-G-3) engaged a formation of I-15s. Although CR.32 (3-100) pilot Enrique Munaiz de Brea (4-E-3) lost his life during the action, the Spaniards claimed seven ‘Curtiss fighters’ destroyed. Two of these aircraft were the first successes for alférez Antonio Manrique Garrido (1-E-3) - one I-15 was seen to fall in flames near Mequinenza, while the pilot of the second machine escaped by parachute. The other kills were individually credited to comandante Morato, capitán Julio Salvador (1-E-3), teniente Manuel Vázquez Sagastizábal (1-E-3), teniente Joaquín Velasco Fernández Nespral (7-E-3) and teniente O’Connor (4-E-3).

In the morning on 14 August, Grupos 2-G-3 and 3-G-3 attacked a formation of Ratas, which were pursuing some He 111s over Gandesa. Other Chatos and Ratas later joined in the battle. Totally the Spanish pilots reported 52 I-16s and 28 I-15s (!).This massive formation of Polikarpovs was also targeted by ten Bf 109s.
Group 2-G-3 claimed three Ratas (teniente Miguel García Pardo (2-E-3), teniente Carlos Bayo (2-E-3) and teniente de Hemricourt (2-E-3)) and 3-G-3 claimed two more (comandante Joaquín García Morato and teniente O’Connor Valdivielso (4-E-3)). 2-G-3s record of operations described the combat:

“García Pardo attacked some Ratas which were pursuing an He 111, shooting down one of the which fell near to Mora de Ebro … Teniente Bayo attacked three Ratas and succeeded in destroying one which fell on the edge of the Blanerías mountains. Later he attacked a Chato, but was unable to ascertain whether it was destroyed as damage to his engine forced him to land at Horta…
Teniente de Hemricourt fired at one Rata without any result; and then attacked some Ratas engaged with other Fiats, hitting one which fell in a wood to the north of Reus.”

During the morning on 3 October, comandante Joaquín García Morato led 24 CR.32s from Grupos 2-G-3 and 3-G-3 on an escort mission for Ro.37s on the Ebro front. They encountered 28 I-16s escorting 24 I-15s that had been undertaking strafing attacks, comandante Morato and 12 fighters from 3-G-3 attacking the biplane fighters at low level, two of which were claimed shot down by Tenientes Medizabal and O’Connor (4-E-3). Twelve other fighters from 2-G-3 tackled the I-16s at a higher altitude, but they soon found themselves badly outnumbered.
As the I-15 escuadrillas withdrew towards Republican lines, Morato and his pilots broke off their attacks and gained height in order to aid their compatriots in the struggle against the I-16s. Morato attacked a Rata from the rear, quickly setting it on fire, but at the same time another CR.32 pilot targeted the same I-16 from an acute angle. A 12.7 mm bullet fired by the second Fiat hit the engine of Morato’s fighter, knocking it out. Still some 12 miles behind enemy lines, but at medium altitude, he used all his skills to glide the engineless CR.32 to within sight of the frontline, before he was forced to perform a dead-stick landing in a vineyard. His aircraft suffered no further damage when he landed. This was the only time that Morato was shot down in combat, albeit not through enemy action but accidentally by his wingman during the heat of battle (according to other sources, Morato was shot down by teniente Sirvent Cerrillo).
The fighter shot down by Morato (although not credited to him) was an I-16 Type 10 from 3^a Escuadrilla, and it was seen to explode in mid-air. Another I-16 (CM-061), this time from 7^a Escuadrilla was destroyed over Corbera by teniente de Hemricourt (2-E-3), de Hemricourt seeing its pilot bail out over Republican territory. A third I-16 Type 10 was hit in the propeller and main-wheel doors by bullets from a CR.32 and its pilot crash-landed near Reus, from where it was recovered.
Republican pilots, in return, claimed nine CR.32s shot down, although in actual fact only one had been lost. However, the pilot downed was none other than the commander of Escuadrilla 1-E-3, capitán Julio Salvador (CR.32ter NC 753/3-69), who was shot down after claiming two enemy aircraft. According to Republican witnesses, his CR.32 had been hit near Fayón early on in the engagement with the I-16s. Salvador’s opponent was the second-in-command of Grupo N^o 21, José Maria Bravo Fernández (according to other sources, Salvador was shot down by teniente Francisco Meroño Pellicer, CO 6^a/21, who claimed a CR.32 during the day). The nationalist pilot was taken prisoner by soldiers of the 46th Division of the Popular Army, commanded by the famous communist leader Valentin Gonzalez.
Salvador was eventually set free in France along with other pilot detainees held by the Republicans after four months in prison.
The I-15s of Grupo N^o 26 claimed four CR.32s (three by 1^a/26 and one by 3^a/26) during the day while the I-16s of Grupo N^o 21 claimed nine CR.32s (three by 4^a/21, two by 7^a/21, three by 1^a/21 and one by 6^a/21).
I-16s CM-261 and CM-263 (both from 3^a/21) were destroyed during the day.

He claimed six individual victories between 13 May 1938 and 3 January 1939, downing three I-15s and three I-16s; all of them while flying in 4-E-3.
He also served in 7-E-3.

O’Connor ended the war with 6 biplane victories.

O’Connor later volunteered for combat in Russia during the Second World War and flew Bf 109Es in 15.(Span)/JG 27.

Claims:

Kill no.	Date	Time	Number	Type	Result	Plane type	Serial no.	Locality	Unit
	1938
1	01/08/38		1	I-15	Destroyed	CR.32		near Fayón	4-E-3
2	14/08/38	morning	1	I-16 (a)	Destroyed	CR.32		Gandesa area	4-E-3
3	03/10/38	morning	1	I-15 (b)	Destroyed	CR.32		Ebro area	4-E-3
4	??/??/3?		1	I-16	Destroyed	CR.32			4-E-3
5	??/??/3?		1	I-16	Destroyed	CR.32			4-E-3
6	??/??/3?		1	I-15	Destroyed	CR.32			4-E-3

Biplane victories: 6 destroyed.
TOTAL: 6 destroyed.
(a) Claimed in combat with I-16 from 1^a, 3^a and 4^a Escuadrillas which lost at least one I-16 and got three more damaged while claiming 3 CR.32s and 1 He 111. 2-G-3 claimed three I-16s and 3-G-3 claimed two more while losing one CR.32 and getting 3 more damaged.
(b) Republican pilots claimed at least 13 CR.32s during the day (on all fronts) while losing at least 3 I-16s. Grupos 2-G-3 and 3-G-3 claimed 5 enemy aircraft while losing 1 CR.32.

Sources:
Air Aces - Christopher Shores, 1983 Presidio Press, Greenwich, ISBN 0-89141-166-6
Air War over Spain - Jesus Salas Larrazabal, 1974 Ian Allan Ltd, Shepperton, Surrey, ISBN 0-7110-0521-4
Fiat CR.32 Aces of the Spanish Civil War - Alfredo Logoluso, 2010 Osprey Publishing, Oxford, ISBN 978-1-84603-983-6
Joaquin Garcia-Morato - Best Ace of Spanish Civil War (WWII Ace Stories) - Mihail Zhirohov, 2003
Wings Over Spain - Emiliani Ghergo, 1997 Giorgio Apostolo Editore, Milano
Additional information kindly provided by Alfredo Logoluso and Ondrej Repka.