Polikarpov I-16 and Fokker D.XXI: Winter War Adversaries

2 D.XXI I-16


In 1939 the Soviet Union, despite signing a non-aggression pact with Germany became concerned that the Finnish government may be persuaded by Nazi Germany to allow their forces access to the Soviet Union through Finland.

There was also a perceived threat from an amphibious assault on Leningrad from the Gulf of Finland. In an effort to secure their northern and eastern flanks, the Soviets demanded that the Finns concede territory in the Karelian Isthmus and islands in the Russian sector of the Gulf of Finland as well as a naval base on the southern Finnish coast in order to provide a buffer by which they may better defend themselves. The demands made on Finland by the Soviet Union amounted to no less than 1% of their territory. The Finns refused the Soviet Union’s demands, negotiations broke down and a declaration of war was issued from the Kremlin.

 The Winter War between the Soviet Union and Finland began on 30th November 1939. Air operations were predominantly conducted over the strategically important region of the Karelian Isthmus. The Soviet Union was able to field some 900 combat aircraft, 375 of which were the Polikarpov I-16’s of various types. The modest Finnish Air Force was able to muster fewer than 50 operational fighters (36 Fokker D.XXI and 10 Bulldog biplane fighters), 18 Bristol Blenheim bombers and an assortment of some 60 close-support, reconnaissance and liaison aircraft. As the war progressed, 30 Gloster Gladiator, 24 Gloster Gauntlet, 12 Hawker Hurricane, 30 Morane Saulnier MS.406, 6 Caudron-Renault CR. 714, 35 Fiat G.50 and 44 Brewster Model 239 fighters were acquired, although the latter arrived too late to participate in the Winter War.

Fokker D.XXI (Mercury) & I-16 Type 10
Fokker D.XXI (Mercury) & I-16 Type 10

Despite overwhelming numerical superiority the small Finnish Air Force gave a good account of itself by employing innovative tactics. To aid gunnery the Finns harmonized their gun coverage at 150 yards range, this increased bullet density increasing the impact of short-burst rounds. In addition, the right-hand synchronised machine gun was loaded exclusively with tracer rounds to assist in correcting the bullet stream.

Finnish fighters were often dispersed in small numbers to auxiliary combat airfields. This enabled the Finns to maximise their small numbers and reduced the risk of losing large numbers of assets if a single airfield was rendered inoperable. The fighters were kept warm and covered when not in use enabling them to be scrambled at short notice. Finnish fighters operated in pairs, with the wingman covering the flight leader, whereas the Soviets employed outdated 3-plane fighter doctrine.

The Soviets also deployed their air regiments en-masse in rigid formations. Due to the Polikarpov I-16 having a superior climb rate and far superior turning circle than the Fokker D.XXI, the Finnish D.XXI pilot’s avoided turning fights with the I-16 at all costs. The Finns chose their targets carefully, using ‘pendulum tactics’ by flying high and diving on their targets before recovering to high altitude and repeating the process.

Polikarpov I-16 Type 10
Polikarpov I-16 Type 10

This tactic was particularly effective against the Soviet ‘Spanish ring’ formations in which Russian fighters would fly in a tight wheeling ring, inviting an enemy fighter to join the ring. The enemy fighter would be at a disadvantage by always having Soviet aircraft on their tail when attacking.

The extraordinary success of the Finns against the Soviets can also be explained in the good quality of the well trained Finnish pilots. The comparable performance of Soviet aircraft to the Fokker D.XXI was off-set in favour of the Finns by the adoption of Luftwaffe-style fighter tactics with the use of Schwarms. 4 aircraft in formation each sub-divided into 2 pairs called ‘elements’ with a flight leader covered by a wingman. Inexperienced pilots were paired with experienced pilots as opposed to Soviet air combat tactics being predictable with en-masse air regiments being deployed in ridged formations, allowing the Finns the opportunity to range above their opponents and choose their targets before attacking and disengaging.

Similarly, they were operating over home territory, thus a damaged aircraft or downed pilot could be retrieved to fight another day. The Soviets were also disadvantaged in having to waste time transiting to and from the combat area.

Finnish command and control was an additional asset. Pilots could communicate with each other and the ground via P-12-17/1 radios, whereas the Soviets had to rely upon outdated hand-signals to communicate between aircraft.

Fokker D.XXI (Mercury)
Fokker D.XXI (Mercury)

The principal Soviet fighter aircraft of the Winter War was the Polikarpov I-16. The Type 10 was first introduced during 1937. It was a modern and revolutionary design when it was first introduced, with an excellent rate of climb and superior maneuverability. The Type 10 differed from its predecessors in having the new M-25V 750hp engine, the wing was re-designed to include landing flaps. Two 7.62 mm ShKAS machine guns were added on top of the engine with two corresponding fairings on the engine cowling. The cockpit was improved and the canopy was re-designed with an all-glass single piece windscreen ahead of the open cockpit.

Had the Soviet pilot’s been able to use the formidable flight characteristics of the I-16 to their advantage and employ more modern fighter tactics, the outcome of the Winter War may have been very different. However, the Red Air Force command structure was disastrous. A ‘Dual Command’ or ‘Collegiate’ control system was introduced in 1937. Each fighter or bomber regiment was assigned a ‘Political Commissar’ with equal rank to the Regiment Commander, each tactical plan and decision had to be approved by the Commissar before it could be implemented.

I-16 4

These problems were further compounded by the fact that each Air Regiment operated as an autonomous ‘Air Army’. Air Regiments would regularly operate independently of each other, not share strategic information and in some cases not communicate with each other in the operational area at all.

The Fokker D.XXI’s of the Finnish Air Force would benefit greatly from these shortcomings and from the use of high speed climbing and diving tactics against the more manoeuvrable Polikarpov I-16 of the Red Air Force. By not engaging the Soviets on their terms, the Finns levelled the 10 to 1 fighter odds that they faced in the air.

I-16 7

During the 1930’s the Soviet Union went through a massive re-armament programme and it became clear to the Finnish establishment that they would need a modern front-line fighter aircraft to meet this threat.

The Finnish Air Force had an established record of aircraft procurement with the Fokker aircraft factory having purchased the Fokker D-10, the Fokker CVE and CVD during the 1930’s. Finland became the first export customer for the type, signing a deal for seven aircraft with a license for 14 more on the 18th November 1937.

The procurement process for the Fokker D.XXI began on August 27th 1937, when Finnish Captain G.E. Magnusson flew 9 test flights in Fokker D.XXI FR-76 at the Fokker aircraft factory. He flew a rigorous test profile with the Fokker D.XXI noticing that it was possible to disengage quickly from an opponent by executing a fast dive. A tactic that would serve Finnish fighter pilots well during the coming Winter War. The fighters were delivered from Amsterdam on October 12th 1937, arriving in Finland between the 4th and 13th November. Just 17 days before the beginning of the Winter War.

The Mercury VIII powered Fokker D.XXI had a maximum speed of 460km/h (286mph), a cruising speed of 429km/h (267mph) and a maximum ceiling of 11,350m (37,238ft.). Time to an altitude of 6000m (19,685ft) was 7 minutes and 30 seconds.


Whilst this performance was by no means remarkable, the Fokker was rugged, reliable and ideally suited to the cold climate experienced at the outbreak of hostilities between Finland and the Soviet Union on the 30th November 1939. In addition, the Fokker D.XXI was well matched against the Polikarpov I-16.

The Mercury VIII Fokker D.XXI’s were armed with two 7.7mm Vickers machine guns in the forward fuselage and one in each wing. These weapons when used in combination with the Goertz optical tube-sight Revi 3C or D gunsight, proved a good arrangement against the Four ShKAS machine guns of the Polikarpov I-16.

In spite of the odds that the Finnish Air Force and in particular the Fokker D.XXI faced at the beginning of the Winter War, Finnish fighters shot down a confirmed 200 Soviet aircraft whilst losing 62 of their own. The Finnish Air Force through an astute procurement programme increased in size by 50% by the end of the Winter War on March 13th 1940.


A further 300 Soviet aircraft were bought down by Finnish anti-aircraft defenses. Lack of fuel, inclement weather, poor tactics and leadership further hampered Soviet attempts to occupy Finland. Indeed, Finland remains the only country other than the United Kingdom during World War Two that was not occupied by the forces attempting to invade it.

The Finnish Air Force flew a total of 5900 combat missions during the Winter War, 3900 of these were intercept missions. The Soviet Union flew a staggering 44000 sorties. The Finnish Air Force dispersed their Fokker DXXI’s to forward air bases and only attacked select formations of Soviet aircraft using high speed hit and run tactics refusing to engage the Soviets on their terms.

At the conclusion of the Winter War and under the terms of the Moscow Peace Treaty, Finland was required to cede 10% of its territory to the Soviet Union. Finland however, against extraordinary odds remained an independent nation.

Total war losses for the three month and two week long Winter War were: 200,000 dead for the Soviet Union. 25,000 Dead for Finland.

6 D.XXI & I-16

General Characteristics Fokker D.XXI (Mercury)


  • Crew: 1
  • Length: 8.2 m (26 ft 11 in)
  • Wingspan: 11 m (36 ft 1 in)
  • Height: 2.92 m (9 ft 7 in)
  • Wing area: 16.2 m2  (174 sq ft)
  • Empty weight: 1,594 kg  (3,514 lb)
  • Gross weight: 1,970 kg  (4,343 lb)
  • Powerplant: 1 × Bristol Mercury VIII 9-cyl. air-cooled radial piston engine, 620 kW (830 hp)


  • Maximum speed: 460 km/h (286 mph; 248 kn)
  • Cruising speed: 429 km/h (267 mph; 232 kn)
  • Never exceed speed: 700 km/h (435 mph; 378 kn)
  • Range: 930 km (578 mi; 502 nmi)
  • Service ceiling: 11,350 m (37,238 ft) service ceiling
  • Time to altitude: 6,000 m (19,685 ft 0 in) in 7 min 30 sec
  • Power/mass: 0.309 kW/kg (0.188 hp/lb)


  • 4 × 7.7 mm (0.303 in) Vickers Machine Guns

General Characteristics Polikarpov I-16 Type 10

I-16 10

  • Crew: One
  • Length: 6.13 m (20 ft 1 in)
  • Wingspan: 9 m (29 ft 6 in)
  • Height: 3.25 m (10 ft 8 in)
  • Wing area: 14.5 m² (156.1 ft²)
  • Empty weight: 1,327 kg (2,925 lb)
  • Loaded weight: 1,716 kg (3,783 lb)
  • Powerplant: 1 × Shetsov M-25V supercharged air-cooled radial engine, 820 kW (750 hp) driving a two-blade propeller


  • Maximum speed: 438 km/h at 3,000 m (9,845 ft)
  • Range: 525 km (326 mi)
  • Service ceiling: 9,700 m (3182 ft)
  • Rate of climb: 10.7 m/s (35 ft 1’)
  • Wing loading: 134 kg/m² (27 lb/ft²)
  • Power/mass: 346 W/kg (0.21 hp/lb)
  • Time to altitude: 6.9 minutes to 5,000 m      (16,405 ft)


  • 4 × fixed forward-firing 7.62 mm (0.30 in) ShKAS machine guns. 2 in upper cowling, 2 in wings.


  • Suomen Ilmavoimien Historia 3A, Fokker D.XXI (Mercury) by Kalevi Keskinen & Kari Stenman. Hobby-Kustannus Oy Press.
  • Suomen Ilmavoimien Historia 18, LeR3 by Kalevi Keskinen & Kari Stenman. Hobby-Kustannus Oy Press.
  • Suomen Ilmavoimien Historia 23, SOTAMAALAUS/WARPAINT by Kalevi Keskinen & Kari Stenman. Hobby-Kustannus Oy Press.
  • VVS Research Page by Massimo Tessitori; http://mig3.sovietwarplanes.com/
  • ‘The Battles of the Winter War’ by Sami Korhonen; http://www.winterwar.com/

Richard Reynolds.




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