Mario Viola was from Rome.

Capitano Viola took part in the Spanish Civil War using the nom de guerre ’Viotti’.

Aniene delivered 12 more CR.32s during a voyage from La Spezia that ended on 4 February 1937. With this shipment arrived squadriglia commander Capitano Viola (’Viotti’) and an additional 11 pilots – five Sottotenenti and six Sottufficiali.

With the arrival of these new fighters there were now sufficient aircraft in-theatre to organise the CR.32 stormo into two gruppi of three squadriglie each. These took the form of the already established I Gruppo (formerly Gruppo Caccia di Torrijos) (CO Maggiore Tarcisio Fagnani) and including the reformed:

1^a Squadriglia (CO Tenente Enrico Degli Incerti from 15 January)
2^a Squadriglia (CO Capitano Guido Nobili)
3^a Squadriglia (CO Tenente Corrado Ricci (followed by Capitani Luigi Lodi and Viola)

4^a Squadriglia (CO Capitano Vincenzo Dequal)
5^a Squadriglia (CO Capitano Armando François from 19 January)
6^a Squadriglia (initially remained in reserve, although it was later commanded by Tenente Antonio Larsimont Pergameni)

When the Nationalist attack on the Basque Country began in the end of March 1937, I Gruppo was moved north and 3^a Squadriglia was stationed at Vitoria.
The 3^a Squadriglia was commanded by Capitano Viola who led the 1st Flight of five aircraft (with reserve pilots) usually including Tenente Luigi Mariotti, Ottorinio Cappellini, Giannoti (”Vitullo”), Curilli, Sartori and Romagnoli.
The 2nd Flight was led by Tenente Corrado Ricci and usually included (with reserve pilots) Tenente Giuseppe Mollo, Sergente Maggiore Guido Presel, Sergente Maggiore Brunetto di Montegnacco, Eugenio Salvi, Aldo Galadini, Bernardino Serafini and Guido Pongiluppi.

On 22 April 1937, the Aviazione Legionaria CR.32 units were reorganised and increased in size. I and II Gruppi were disbanded, re-designated and replaced by two Gruppi that each controlled three Squadriglie as before. A third new gruppo the VI, was also formed.
The XVI Gruppo Caccia under the command of Maggiore Giuseppe Casero (’Casetti’) included:

24^a Squadriglia (formerly 4^a Squadriglia, CO Capitano Bruno Brambilla)
25^a Squadriglia (formerly 5^a Squadriglia, CO Capitano Armando François)
26^a Squadriglia (formerly 2^a Squadriglia, CO Capitano Viola)

18^a Squadriglia (formerly 3^a Squadriglia, CO Capitano Guido Nobili)
19^a Squadriglia (formerly 1^a Squadriglia, CO Tenente Enrico Degli Incerti)
20^a Squadriglia (formerly 6^a Squadriglia, CO Capitano Antonio Larsimont Pergameni)

Between 16:00-17:15 on 4 June 1937 on the Northern Front, ten CR.32s from 26^a Squadriglia, led by Capitano Viola flying between Amorebieta and the Murguia front at 5 000 meters altitude, clashed with 17 I-15s between the Republican Escuadrilla Baquedano’s two bases (San Juan de Somorrostro and Sondica). Italian pilots claimed to have shot down seven “Curtiss fighters” in the Sondica area without loss, Capitano Viola being credited with two individual victories, Sergente Maggiore Guido Presel one Sergente Maggiore Guido Pongiluppi (CR.32 NC.128) one, Sergente Italo De Bernardinis one, Sergente Maggiore Aldo Galadini one and Giannoti one.
Although both sides drastically overestimated their claims, Spanish I-15 pilot Marcelino Alonso Romero from Escuadrilla Baquedano did indeed lose his life during this encounter.

When the Republican offensive towards Brunete started on 6 July 1937, the defence of the central front was supported by just the two CR.32 squadriglie present in this area at Torrijos-Barcience; the 19^a and 20^a Squadriglie from XXIII Gruppo, commanded by Maggiore Andrea Zotti, with squadriglia commanders Capitani Enrico Degli Incerti and Antonio Larsimont Pergameni.
Capitano Guido Nobili’s 18^a Squadriglia was transferred in from Soria to reinforce these units, thus completing the makeup of the gruppo. The XXIII Gruppo now had 29 CR.32s available, but only 17 of these remained serviceable following a series of actions on 6-7 July.
Maggiore Giuseppe Casero’s XVI Gruppo (24^a, 25^a and 26^a Squadriglie, led by Capitani Bruno Brambilla, Armando François and Viola, respectively, although the latter was recalled to Italy and replaced by Tenente Corrado Ricci on 11 July) arrived at Torrijos-Barcience from Ávila three days later, as did six CR.32s from capitan Morato’s Grupo 2-G-3.

After the end of the battle of Brunete on 26 July, the XXIII Gruppo Caccia was awarded the Medalla Militar Colectiva (Collective Military Medal) by general Franco following its performance during the first few days of the Republican offensive. Two pilots from the unit had lost their lives in combat and three had been wounded, yet the gruppo continued to engage a numerically superior enemy until reinforcements were brought in.

Viola claimed 2 biplane victories during the Spanish Civil War.

Claims:

Kill no.	Date	Time	Number	Type	Result	Plane type	Serial no.	Locality	Unit
	1937
1	04/06/37	16:00-17:15	1	I-15 (a)	Destroyed	Fiat CR.32		Sondica area	26a Squadriglia
2	04/06/37	16:00-17:15	1	I-15 (a)	Destroyed	Fiat CR.32		Sondica area	26a Squadriglia

Biplane victories: 2 destroyed.
TOTAL: 2 destroyed.
(a) 26^a Squadriglia claimed 7 I-15s without losses but only 1 can be verified (pilot KiA).

Sources:
Aerial War in Spain: Chronicle of air battle 1936-1939 – Sergey Abrosov, 2008
Courage Alone - Chris Dunning, 1998 Hikoki Publications, Aldershot, ISBN 1-902109-02-3
Elenco Nominativo dei Militari dell' A. M. Decorati al V. M. Durante it Periodo 1929 - 1945 2 Volume M - Z
Fiat CR.32 Aces of the Spanish Civil War - Alfredo Logoluso, 2010 Osprey Publishing, Oxford, ISBN 978-1-84603-983-6
Guido Pongiluppi: Pilota Mantovano, Dal Cielo Di Campoformido A Quelli Di Spagna E Malta - Renato Zavattini and Antonio Inguscio, 2021 IBN Instituto Bibliografico Napoleone, ISBN 9788875655389
Regia Aeronautica: The Italian Air Force 1923-1945 - An Operational History - Chris Dunning, 2009 Ian Allan Publishing, Hersham, Surrey, ISBN 978-1-906537-02-9