On 30 October 1940, Brown was posted to 112 Squadron as a Pilot Officer.

Together with the Squadron he took part in the Greek campaign.

On 11 March, 15 of 112 Squadrons aircraft were over the front, this time to escort 211 Squadron Blenheims on a raid in the Bousi area. An estimated 40-50 G.50bis were reported patrolling in the area and nine of these fighters from the 24^o Gruppo (led by Maggiore Cesare Valente) engaged the formation, claiming a Blenheim and one Gladiator shot down. The British fighters turned on the attackers and claimed seven shot down, one probable and seven damaged without loss. The claims were made by Flight Lieutenant Joseph Fraser (one and one damaged), Flying Officer Edwin Banks (one and two damaged), Flying Officer Richard Acworth (one), Flying Officer Homer Cochrane (one), Flying Officer Brown (one damaged), Flying Officer Henry Harrison (one), Pilot Officer Neville Bowker (one), Pilot Officer Gerald Westenra (one), Flight Lieutenant Charles Fry (one probable and one damaged), Squadron Leader Harry Brown (one damaged) and Flying Officer Denis Herbert Vincent Smith (one damaged). Bowker and Westenra where both involved in only their second engagements since joining the unit from Flying Training School.
Two G.50bis went down at once. Maggiore Valente and Sergente Luigi Spallacci both were killed, while Sergente Bruno Fava and Sergente Maggiore Ermes Lucchetta were both wounded and crash-landed their Fiats on their bellies. MC.200s of the 22^o Gruppo may also have become involved, for Sergente Anselmo Andraghetti of 369^a Squadriglia was lost, the cause not being ascertained.
After the combat Banks remarked that the G.50s must be armoured as they stood up to so much punishment. Fry reported that he attacked a G.50, which spun slowly twice then flattened out and turned slowly onto its back with smoke coming from it. It went into cloud and he didn't see it again. He also attacked another G.50bis of 24^o Gruppo, which went over onto its back and flew inverted into cloud. Squadron Leader Brown emptied all his rounds into a G.50 without effect. No doubt the all-metal construction of these monoplane fighters helped to hold them together.

During the afternoon of 13 March Squadron Leader H. L. I. Brown led 14 Gladiators from 112 squadron and six of 33 Squadron's Hurricanes off from Paramythia for an offensive patrol over the Kelcyre area. Approaching Kelcyre at 15:30 on an altitude of 17,000 feet an estimated 14 S.79s were seen - aircraft from 104^o Gruppo B.T. - with an escort identified as 20 G.50bis and 20 plus CR.42s.
Three of the Hurricanes attacked the mass of fighters, followed by the Gladiators, and many individual dogfights ensued. Squadron Leader Brown attacked the leading fighter of a flight of three, but it evaded him successfully. He then got on the tail of another, which turned and dived and eventually crashed; he claimed a G.50 and another damaged. Flight Lieutenant Joseph Fraser attacked a CR.42, which had not seen him. He reported that it burst into flames and crashed near Bousi. Two more were claimed destroyed by Flying Officer Homer Cochrane and Pilot Officer Jack Groves, while Pilot Officers Neville Bowker and D. G. H. McDonald each claimed a probable CR.42.
The Gladiators reformed, then spotted about 30 more CR.42s with 38^o Stormo BR.20s. Seven of Flight Lieutenant Charles Fry’s ‘C’ Flight pilots went after the bombers, while Flight Lieutenant Fraser’s ‘A’ Flight tackled the fighters, claiming seven more shot down. Fraser attacked a CR.42, which flick-rolled and dived away. He followed it down and got in two long bursts after which the enemy aircraft levelled off and lost speed, with the pilot slumped forward in the cockpit. The aircraft then dived vertically into the ground north of Corovode. Fraser then climbed back up to 8,000 feet and got on the tail of another CR.42 firing at it continuously until it burst into flames and was destroyed. Fraser’s own aircraft was badly shot up, as was that of Pilot Officer Groves (after having claimed a second CR.42 and one damaged), but both managed to get back to base. Flying Officer Cochrane claimed two more CR.42s while Pilot Officer P. C. L. Brunton and Flying Officer Brown each claimed a CR.42.
The ‘G.50bis’ seem to have been 22^o Gruppo Macchi MC.200s, 11 of which accompanied 18 CR.42s from the 160^o Gruppo over the front. The Italian pilots claimed four Gladiators and one Hurricane shot down, losing just two CR.42s flown by Tenente Gualtiero Bacchi and Sottotenente Enzo Torroni (both from 375^a Squadriglia), but no MC.200s. It seems that Capitano Vittorio Minguzzi claimed a probable Gladiator in this combat.
Although no claims were made against the bombers on this occasion, several were in fact hit and damaged, a number of crewmen being wounded.
In his combat report Fraser commented that the CR.42 pilots always tried to flick-roll when attacked.

Brown was transferred from 112 Squadron on 14 April 1941.

Brown ended the war with 1 biplane victory, this one being claimed while flying Gloster Gladiators.

Claims:

Kill no.	Date	Number	Type	Result	Plane type	Serial no.	Locality	Unit
	1941
	11/03/41	1	G.50 (a)	Damaged	Gladiator		Bousi area	112 Squadron
1	13/03/41	1	CR.42 (b)	Destroyed	Gladiator		Kelcyre area	112 Squadron

Biplane victories: 1 destroyed, 1 damaged.
TOTAL: 1 destroyed, 1 damaged.
(a) Claimed in combat with G.50bis from 24^o Gruppo. 112 Squadron claimed seven shot down, one probable and seven damaged without loss. 24^o Gruppo lost four aircraft (Maggiore Cesare Valente and Sergente Luigi Spallacci were killed and Sergente Bruno Fava and Sergente Maggiore Ermes Lucchetta were wounded) while claiming a Blenheim and one Gladiator shot down.
(b) Claimed in combat with MC.200s from 22^o Gruppo and CR.42s from 160^o Gruppo. 112 Squadron claimed 10 CR.42s destroyed, 2 probables and 1 damaged and 1 ‘G.50bis’ and 1 damaged without losses. The Italian pilots claimed four Gladiators and one Hurricane shot down, losing two CR.42s flown by Tenente Gualtiero Bacchi and Sottotenente Enzo Torroni (both from 375^a Squadriglia), but no MC.200s.

Sources:
Air war for Yugoslavia, Greece and Crete - Christopher Shores, Brian Cull and Nicola Malizia, 1987 Grub Street, London, ISBN 0-948817-07-0
Shark Squadron - The history of 112 Squadron 1917-1975 - Robin Brown, 1994 Crécy Books, ISBN 0-947554-33-5
Additional information kindly provided by Robert Brown and Carlo Minguzzi.