Maksimov was a member of the 96 Otdelnaya Aviaeskadrilya (OIAE - independent squadron). The commanding officer of this unit was Kapitan Alexandr Korobitzin. In June 1941 the unit was based on Ismail airfield and equipped three Polikarpov I-153s and fourteen Polikarpov I-152s.

During the Axis attack on Soviet Union in June 1941 Rumanian forces attacked the part of the front that included Izmail.

At 14.00 on 22 June 1941, fourteen I-152s and three I-153s of 96 OIAE attacked fourteen Romanian PZL P.37s of Escadrila 76 and 77 over the Danube in southern Bessarabia, claiming five of them shoot down (including two by I-152s). The 96 OIAE commander Kapitan Alexandr Korobitzin and Leytenant Maksimov (whose victim fell into the Danube River) each claimed a destroyed. A shared was claimed by the pilots in Maksimov's flight. One shared was claimed by Starshiy Leytenant Lavrentiy Borisov, deputy commander of 96 OIAE, and Leytenant Nikolai Cherkasov. The fifth, finally, was claimed as a shared between Leytenant Vasiliy Kuroedov (flight commander), Leytenant Leonid Khomutov, Leytenant Alexandr Evstigneev and Leytenant Shota Gogmachadze.
The P.37s were escorted by six Rumanian Hurricane Is, which claimed four victories. The Soviet forces, however, didn't sustain any losses but in the combat was Leytenant Boris Maslov slightly wounded in left shoulder while flying an I-152s.
Three of their victories were later confirmed to the 96 OAE pilots. Fortelor Aeriene Regal ale România (FARR - Royal Romanian Air Force) lost 11 planes this day but only two of them were P.37 Los and these were claimed to have been shot down by anti-aircraft fire.

On 28 June, Maksimov intercepted Rumanian He112Bs, which attacked Kiliya and Ismail. He shot down two of them. One of the Romanian pilots was killed and the other was wounded but he successfully baled out of his stricken Heinkel and landed on the Romanian side of the front. Escadrila 51 (51 Squadron) of the FARR lost aircraft no. 6 and 8 in this combat. Romanian records claims that no. 8, which was flown by Sublocotenent aviator Constantin Smeu, was hit by anti-aircraft fire while providing long range fighter escort to bombers attacking Kiliya and Ismail Harbours on the left bank of the Danube River. On its way back, the He 112 ran out of fuel and was forced to land 16km from Râmnicul Savat in Moldavia. During the rough wheel-up landing, the central fuel tank exploded and the already wounded pilot suffered burns. He was hurried to a nearby hospital were he died on 2 July. The second Heinkel with no. 6, which was flown by Sublocotenent aviator Constantin Stancu crash-landed and caught fire on Romanian territory following a dogfight with Soviet fighters with the pilot wounded.

He was then transferred to the 26 IAP, which operated on the Leningrad Front.

On the evening of 4 April 1942 more than one hundred aircraft from KG 1, KG 4, StG 2 and JG 54 joined together in a single concentration to attack Soviet ships on the Neva River in Leningrad in a mission code named ”Eisstoss” (Ice Thrust).
VVS-KBF scrambled 3 and 4 GIAPs and 71 IAP, while Leningrad PVO scrambled 26 IAP against the raid. The Soviet fighters were however intercepted by the escorting Bf109s at a lower altitude and suffered heavily without being able to deal the raiders any losses.
During the drawn out air combat, JG54 claimed twenty Soviet fighters shot down – including the 2000th victory by JG 54, claimed by Oberfeldwebel Rudolf Klemm (totally 42 victories). One of the shot down and killed pilots were Leytenant Maksimov, who was shot down over Seiskor Island in the Gulf of Finland.
The Soviets reported 18 German aircraft shot down including four by Aleksandr Baturin, but this is totally unsupported with Luftwaffe loss statistics, according to which not a single German aircraft was lost over Leningrad on this date.
The German raid was however a failure when the Soviet ships only suffered minor damages.

At the time of his death, Maksimov was credited with 3 biplane victories.

Claims:

Kill no.	Date	Time	Number	Type	Result	Plane type	Serial no.	Locality	Unit
	1941
1	22/06/41	14:00	1	Romanian bomber (a)	Destroyed	I-152 (b)		Danube River	96 OIAE
2	28/06/41		1	He112 (c)	Destroyed	I-153		Ismail area	96 OIAE
3	28/06/41		1	He112 (d)	Destroyed	I-153		Ismail area	96 OIAE

Biplane victories: 3 destroyed.
TOTAL: 3 destroyed.
(a) Claimed in combat with PZL P.34s of Escadrila 76 and 77. 96 OIAE claimed five victories but only two Rumanian aircraft were lost and theses were claimed to have been shot down by AA fire.
(b) This victory may have been claimed while flying an I-152 or an I-153.
(c) Probably He 112 no. 8 of Escadrila 51 (51 Squadron) of the FARR flown by Second Lieutenant Constantin Smeu who was killed when he crash-landed.
(d) Probably He 112 no. 6 of Escadrila 51 (51 Squadron) of the FARR flown by Sub Lieutenant Constantin Stancu who was wounded.

Sources:
Black Cross/Red Star Volume II - Christer Bergström and Andrey Mikhailov, 2001 Pacifica Military History, ISBN 0-935553-51-7
From Barbarossa to Odessa: Volume 1 – Dénes Bernád, Dmitriy Karlenko and Jean-Louis Roba, 2007 Ian Allan Publishing Ltd, ISBN 978-85780-273-3
Heinkel He 112 in action - Dénes Bernád, 1996 Squadron/Signal Publications, Carrollton kindly provided by Ondrej Repka
Morskie letchiki v oborone Odessy - A.P. Dorokhov, 1982 Mayak, Odessa, kindly provided by Yuri Shakhov
Rumanian Air Force: The Prime Decade, 1938-1947 - Dénes Bernád, 1999 Squadron/Signal Publications, Carrollton, ISBN 0-89747-402-3
Sovetskaya aviacia nad morem - Sergey Bogatyrev, 1999 Aviacia i Vremya 3/99, Ukraine kindly provided by Ondrej Repka
Vtorzhenye, part III - Dmitriy Khazanov, 1996 Aviacia i Vremya 5/96, Ukraine kindly provided by Ondrej Repka
Additional information kindly provided by Mirek Wawrzynski