Kapitan I. I. Popov served as CO of the 3rd eskadrilya of 49 IAP during the Winter War in 1939-40. This unit was at the time equipped with Polikarpov I-153s.

At 16:00 on 20 January 1940, kapitan Popov, kapitan Aleksey Korochantsev and starshiy leitenant F. M. Fatkulin of the 3rd eskadrilya of 49 IAP claimed two shot down Finnish Fokker C.Xs 2-3km south-east of Nietjärvi.
These losses can’t be verified with Finnish records.

At 16:45 on 22 January 1940, 49 IAP claimed one Fokker D.XXI and one biplane fighter shot down over Sortavala.
These two claims were shared between starshiy leitenant Ivan Murazanov (I-16), starshiy leitenant I. S. Savushkin (I-16), mladshiy leitenant Sergey Goriunov (I-16), polkovnik Vladimir Kitayev (I-153), kapitan Popov (I-153) and starshiy leitenant Vladimir Nikolayevich Peshkov (I-153).
These claims can’t be verified with Finnish records and it seems that in fact the biplane was a Soviet I-15bis flown by mladshiy leitenant A. F. Rumayantsev, who became MIA.

On 29 January, three I-153s led by kapitan Popov reportedly attacked and destroyed an armoured train at Impilahti.

Popov ended the war with 4 shared biplane victories.

Claims:

Kill no.	Date	Time	Number	Type	Result	Plane type	Serial no.	Locality	Unit
	1940
	20/01/40	16:00	1/3	Fokker C.X (a)	Destroyed	I-153		2-3km SE Nietjärvi	3/49 IAP
	20/01/40	16:00	1/3	Fokker C.X (a)	Destroyed	I-153		2-3km SE Nietjärvi	3/49 IAP
	22/01/40	16:45	1/6	Fokker D.XXI (b)	Destroyed	I-153		Sortavala	3/49 IAP
	22/01/40	16:45	1/6	Biplane fighter (c)	Destroyed	I-153		Sortavala	3/49 IAP

Biplane victories: 4 shared destroyed.
TOTAL: 4 shared destroyed.
(a) Claim can’t be verified with Finnish records.
(b) Claim can’t be verified with Finnish records.
(c) Claim can’t be verified with Finnish records.

Sources:
All aces of Stalin 1936-1953 – Mikhail Bykov, 2014
Red Stars 7 - Talvisota Ilmassa - The Winter War In the Air - Carl-Fredrik Geust, 2011 Apali Oy, Tampere, ISBN 978-952-5877-04-5
Red Wings in the Winter War 1939-1940 - Carl-Fredrik Geust, 2020 MMP books, ISBN 978-83-65958-51-8
Soviet Aces 1936-1953
Soviet Fighter Pilots 1936-1953 - Mikhail Bykov