Theron joined the South African Permanent Force and attended the Military College 1939 - 1940. He received his wings on 25 April 1940.

On 13 May 1940 he was posted to 1 SAAF Squadron. This unit took part in the East African campaign, initially using Gloster Gladiators.

On 20 September Major Schalk van Schalkwyk with Second Lieutenants Theron and Andrew Duncan strafed Tessenei airfield. A Ca.133 was reported damaged on the ground.

On an early patrol on 4 November over Metemma three Gladiators from 1 SAAF Squadron were attacked from above by four CR.42s from 412^a Squadriglia. The South Africans swiftly turned the tables, Lieutenant Theron shooting down one from which the pilot baled out, while Captain Brian Boyle and Lieutenant Andrew Duncan claimed two more (Duncan’s was not confirmed). The Italian pilots claimed to have shot down one Gladiator and reported the loss only of the aircraft shot down by Theron.

In December 1940 1 SAAF Squadron started to receive Hurricanes, which the unit operated together with the Gladiators until all of these aircraft was replaced in the end of February 1941.

At 13:00 on 16 December Lieutenants Theron and Servaas de K. Viljoen and Second Lieutenant Jarvis scrambled from Azaza to intercept bombers. One CR.42 was seen, but it saw them early enough, outdistancing their pursuit in a dive.

On the morning on 27 January 1941, six Hurricanes and six Gladiators of 1 SAAF Squadron, using Sabderat as an advanced landing ground for refuelling, attacked Gura airfield during the day, many aircraft being seen there. While Major Wilmot, Lieutenant Theron and a third pilot remained above as top cover, the other nine strafed, claiming hits on nine S.79s, seven S.81s and three Ca.133s.
The Gladiators taking part in the strafe were led by Captain Brian Boyle (Gladiator N5815) and the other five pilots were Lieutenants Servaas de K. Viljoen, Robin Pare, Andrew Duncan, John Coetzer and Taylor. Hurricane pilots included Major Wilmot, Captain K. W. Driver, Lieutenant John Hewitson and Lieutenant Theron.
After the strafe at Gura, Captain Driver and Lieutenant Hewitson continued to Adi Ugri where Driver strafed four more S.81s, claiming damaged to two of them. Hewitson meanwhile strafed other ground target.
The Italians reported that three S.79s and four S.81 were substantially damaged.

At 12:30 on 20 February, Lieutenants Robin Pare, John Coetzer, Theron and Dirk C. Uys took off to attack Massawa aerodrome (and Decamere and Adi Ugri?). They found and damaged four CR.42s and a Ca.133.
It seems that in fact four CR.42s, two Ca.133 and two S.81s were damaged in this raid.

Air reconnaissance had reported that new CR.42s being assembled at Massawa after delivery by transport aircraft, and at 08.00 on 21 February Major Lawrence Wilmot from 1 SAAF Squadron took off from Kassala with Captain Brian Boyle and Lieutenants Robin Pare, John Coetzer, Theron, Servaas de K. Viljoen and E. A. “Tuppy” Jarvis. The Hurricanes refuelled en route at Agordat and took off at 11:00, attacking Massawa at midday. A small number of aircraft was seen outside the hangars, but the number inside was not known, so all six hangars were attacked, the pilots approaching at zero feet and firing directly into them; all were left in flames, the roof of one being blown right off by Major Wilmot. Six Ca.133s and a CR.42 were strafed in the open, and claimed in flames, while Lieutenant Robin Pare wiped out an anti-aircraft position and crew, which were firing on Major Wilmot. His guns then jammed but he continued to make dummy runs on the AA posts, being the last to leave the area. Lieutenant John Coetzer was however shot down and killed by AA fire, his Hurricane (V7658) crashing in flames.
In fact, three Ca.133s and two S.81s, all of which had been damaged the previous day, were destroyed, and one more of each was damaged.

In the morning on 22 March two Hurricanes of 1 SAAF squadron escorted six Wellesleys and six Blenheims to Asmara, but south of the town three 412^a Squadriglia CR.42s were seen, one of which at one disappeared. Lieutenant Theron attacked the leading fighter and his fire killed the pilot, the aircraft crashing in flames 20 miles south-east of the town. A second CR.42 was claimed by Lieutenant J. B. White, also reportedly seen to crash.

He left the squadron in April 1941 and was posted to 7 SAAF Squadron in 1942.

On 6 August 1942 12 of 7 SAAF Squadron’s fighters, with six more aircraft from 6 Squadron undertook a strafing attack during which his Hurricane was hit by Flak, obliging him to crash land and become a PoW.

He spent the rest of the war in Stalag Luft III in Germany.

Theron ended the war with 1 biplane victory and a total of 2.

Claims:

Kill no.	Date	Number	Type	Result	Plane type	Serial no.	Locality	Unit
	1940
1	04/11/40	1	CR.42 (a)	Destroyed	Gladiator II		Metemma	1 SAAF Squadron
	1941
	20/02/41	1/4	CR.42 (b)	Shared destroyed on the ground	Hurricane		Massawa	1 SAAF Squadron
	20/02/41	1/4	CR.42 (b)	Shared destroyed on the ground	Hurricane		Massawa	1 SAAF Squadron
	20/02/41	1/4	CR.42 (b)	Shared destroyed on the ground	Hurricane		Massawa	1 SAAF Squadron
	20/02/41	1/4	CR.42 (b)	Shared destroyed on the ground	Hurricane		Massawa	1 SAAF Squadron
	20/02/41	1/4	Ca.133 (b)	Shared destroyed on the ground	Hurricane		Massawa	1 SAAF Squadron
	21/02/41	1/7	Ca.133 (c)	Shared destroyed on the ground	Hurricane		Massawa	1 SAAF Squadron
	21/02/41	1/7	Ca.133 (c)	Shared destroyed on the ground	Hurricane		Massawa	1 SAAF Squadron
	21/02/41	1/7	Ca.133 (c)	Shared destroyed on the ground	Hurricane		Massawa	1 SAAF Squadron
	21/02/41	1/7	Ca.133 (c)	Shared destroyed on the ground	Hurricane		Massawa	1 SAAF Squadron
	21/02/41	1/7	Ca.133 (c)	Shared destroyed on the ground	Hurricane		Massawa	1 SAAF Squadron
	21/02/41	1/7	Ca.133 (c)	Shared destroyed on the ground	Hurricane		Massawa	1 SAAF Squadron
	21/02/41	1/7	CR.42 (c)	Shared destroyed on the ground	Hurricane		Massawa	1 SAAF Squadron
2	22/03/41	1	CR.42 (d)	Destroyed	Hurricane		20m SE Asmara	1 SAAF Squadron

Biplane victories: 1 destroyed.
TOTAL: 2 destroyed, 12 shared destroyed on the ground.
(a) Claimed in combat with CR.42s from 412^a Squadriglia, which lost one aircraft while claiming a Gladiator. 1 SAAF Squadron claimed three Fiats without losses (of which two were confirmed).
(b) Four CR.42s, two Ca.133 and two S.81s damaged on the ground.
(c) Three Ca.133s and two S.81s, all of which had been damaged the previous day, were destroyed, and one more of each was damaged.
(d) Claimed in combat with CR.42s from 412^a Squadriglia.

Sources:
Dust Clouds in the Middle East - Christopher Shores, 1996 Grub Street, London, ISBN 1-898697-37-X
Gloster Gladiator Home Page - Alexander Crawford.
Springbok Fighter Victory: East Africa Volume 1 1940 – 1941 – Michael Shoeman, 2002 African Aviation Series No. 11, Freeworld Publications CC, ISBN 0-958-4388-5-4
Those Other Eagles – Christopher Shores, 2004 Grub Street, London, ISBN 1-904010-88-1