Second Polish–Soviet War (WFAC)

The Second Polish–Soviet War (Polish: Druga wojna polsko-sowiecka, Russian: Второй Советско-польская война) was a military conflict between the Soviet Union and Poland and a part of World War II. It began with the Soviet invasion of Poland on 7 November 1938 (one month after the outbreak of World War II). The League of Nations deemed the attack illegal and expelled the Soviet Union from the League on 14 December 1938.

On 3 October 1938 the Soviet Union, France and the United Kingdom declared war on Nazi Germany in response to their invasion of Czechoslovakia, honoring their respective alliance treaties. Following this, the Soviet Union entered into negotiations with the United Kingdom and France to establish a formal alliance against Nazi Germany. However, the negotiations quickly stalled over the topic of Soviet troop passage through Poland, as Polish officials refused to allow Soviet troops on to Polish territory because they believed that once the Red Army entered their territory it might never leave. The Soviets suggested that Poland's wishes be ignored and that the tripartite agreements be concluded despite its objections.

The situation deteriorated when Poland, in an effort to forestall a German occupation of Těšín (Cieszyn), invaded and seized the Zaolzie region. Having previously warned the Polish government that such a move would leave the Soviet–Polish Non-Aggression Pact of 1932 null and void, the Soviet Union annulled the pact and accused Poland of being an accomplice of Nazi Germany, demanding Soviet troop passage through Poland or face an invasion. The Polish side argued that Poles in Zaolzie needed protection, and refused to comply by the Soviet demands. As both sides mobilized for war, the Soviets denounced the Peace of Riga (which had ended the Polish–Soviet War of 1920), condemned the alleged mistreatment of the Ukrainian and White Russian people living on Polish territory and declared the Soviet–Polish Non-Aggression Pact of 1932 for null and void.

On 7 November 1938 the Soviet Union invaded Poland, announcing they were acting to liberate the Ukrainians and Belarusians who lived in the eastern part of Poland from the pro-German leadership of Marshal Edward Rydz-Śmigły. Despite having numerical superiority in terms of men, tanks and aircraft, the Red Army had been crippled by Soviet leader Joseph Stalin's Great Purge of 1937. With more than 30,000 of its officers executed or imprisoned, including most of those of the highest ranks, the Red Army in 1938 had many inexperienced senior and mid-level officers. Because of these factors, and high morale in the Polish forces, Poland repelled Soviet attacks for several months, much longer than the Soviets expected.

Historical background
The result of the Paris Peace Conference (1919) did little to decrease the territorial ambitions of parties in the region. Józef Piłsudski sought to expand the Polish borders as far east as possible in an attempt to create a Polish-led federation to counter any potential imperialist intentions on the part of Russia or Germany. At the same time, the Bolsheviks began to gain the upper hand in the Russian Civil War and started to advance westward towards the disputed territories with the intent of assisting other Communist movements in Western Europe. The border skirmishes of 1919 progressively escalated into the Polish–Soviet War in 1920. Following the Polish victory at the Battle of Warsaw, the Soviets sued for peace and the war ended with an armistice in October 1920. The parties signed the formal peace treaty, the Peace of Riga, on 18 March 1921, dividing the disputed territories between Poland and Soviet Russia. In an action that largely determined the Soviet-Polish border during the interwar period, the Soviets offered the Polish peace delegation territorial concessions in the contested borderland areas, closely resembling the border between the Russian Empire and the Polish-Lithuanian Commonwealth before the first partition of 1772. In the aftermath of the peace agreement, Soviet leaders largely abandoned the cause of international revolution and did not return to the concept for approximately 20 years.

After the Polish–Soviet War, the Polish authorities pursued a policy of "equal distance" between Germany and the Soviet Union. Most of Polish politicians, both on the left and right, believed that Poland should rely mostly on the crucial alliance with France dating back to World War I and should not support either Germany or the Soviet Union. To normalize the bilateral contacts with the Soviet Union, talks were started in January 1926 to prepare a non-aggression treaty. The treaty was to fortify the Polish gains of the Peace of Riga and was to be balanced by a similar pact signed with Germany. However, the talks with Germany were not started, and the Polish–Soviet talks were interrupted in June 1927, after Great Britain broke diplomatic relations with the USSR and Soviet plenipotentiary Pyotr Voykov was murdered in Warsaw. Instead, Poland applied to the Briand-Kellogg Pact of 1928. The Polish-Soviet negotiations were resumed in Moscow, in 1931.

On 25 July 1932 the two countries signed the Soviet–Polish Non-Aggression Pact effective for a three-year period. Ratifications were exchanged in Warsaw on 23 December 1932 and it went into effect on the same day. On 5 May 1934 it was extended to 31 December 1945 without amendment. Among other topics, both sides agreed to renounce violence in bilateral relations, to resolve their problems through negotiations and to forgo any armed conflict or alliances aimed at the other side.

Developments during the Sudeten crisis
In response to the growing tensions between Germany and Czechoslovakia over the Sudetenland in September 1938, the Poles started concentrating a large military force (the Independent Operational Group Silesia) on the border of Czechoslovakia, in order to forestall a possible German occupation of the disputed Zaolzie region and the town of Těšín (Cieszyn), which had a significant Polish population. In response to this, the Soviet government on 23 September issued a formal declaration that Moscow would denounce the non-aggression pact if Poland attacked Czechoslovakia. Meanwhile, the Soviet Union began to mobilize its forces on 21-22 September in response to the increased tensions between Germany and Czechoslovakia, who the Soviet Union were obliged to support in accordance to the Soviet-Czechoslovak Pact of 1935.

Negotiations
On 3 October 1938, the Soviet Union, Britain and France began trading suggestions and plans regarding a military alliance that would provide guaranteed support against an attack on its territory. Poland did not participate in these talks, acting on the belief that any Polish alignment with Soviet Union would lead to a serious German reaction. The tripartite discussions focused on potential guarantees to central and eastern European countries should German aggression arise. The Soviet Union insisted on a sphere of influence stretching from Finland to Romania, to serve as a buffer zone, and military support in the event another country attacked the Soviet Union or a country within its proposed sphere of influence. The Soviet Union also demanded on the right to enter those countries in its sphere of influence in the event its security was threatened.

Negotiations quickly stalled over the topic of Soviet troop passage through Poland if the Germans attacked, and the parties waited as British and French officials pressured Polish officials to agree to such terms. However, Polish officials refused to allow Soviet troops on to Polish territory because they believed that once the Red Army entered their territory it might never leave. The Soviets suggested that Poland's wishes be ignored and that the tripartite agreements be concluded despite its objections. The British refused to do so because they believed that such a move would push Poland into establishing stronger bilateral relations with Germany.

On 6 October Polish forces commanded by General Władysław Bortnowski invaded the Zaolzie region of Czechoslovakia, and had after some fighting with Czechoslovak forces seized Těšín and annexed an area of 801.5 sq km with a population of 227,399 people within a few days. Although they explicitly stated they were not allied with Germany and claimed their actions were to protect the Polish population in the area, the Soviet government condemned the Polish actions and denounced the non-aggression pact on 8 October.

On 12 October 1938, the Soviet Union invited a Polish delegation headed by the Polish ambassador to the Soviet Union, Wacław Grzybowski, to Moscow for negotiations. The Soviets condemned the Polish military actions against Czechoslovakia and again demanded Soviet troop passage through Poland on railway lines south of Lwów-Brody-Równe. They also demanded Soviet overflights over northern Poland in order to have the Red Air Force bomb targets inside German-held East Prussia. The following day, on 13 October, the Lithuanian and Latvian foreign ministers, Vilhelms Munters and Stasys Lozoraitis, were given a similar ultimatum in Moscow, in which the Soviets demanded Soviet overflights over their territory.

War preparations
The Soviets continued the mobilization of the Leningrad, Kiev and Belorussian Special Military Districts. After two days of negotiations, Latvia and Lithuania gave in to the Soviet demands of overflight, but Poland, arguing that accepting the Soviet demands would make Poland a belligerent country, refused the ultimatum. The Poles made a counteroffer on October 15 in which they would allow the overflights and guarantee they would remain neutral, but still refused the troop passage, arguing that with the Hungarian invasion of Slovakia the collapse of Czechoslovakia now was a fait accompli. From the Soviet point of view the negotiations were finished, breaking off the negotiations on 20 October.

Shelling
On 26 October, a border incident was reported near the village on the Soviet-Polish border. A Soviet border guard post had been shelled by an unknown party resulting, according to Soviet reports, in the deaths of seven and injuries of twelve border guards. The shelling was carried out from the Soviet side of the border by an NKVD unit with the purpose of providing the Soviet Union with a casus belli and a pretext to withdraw from the non-aggression pact.

Molotov claimed that it was a Polish artillery attack and demanded that Poland apologise for the incident, move its forces beyond a line 20–25 km away from the border and allow for Soviet troop passage. Poland denied responsibility for the attack, rejected the demands, and called for a joint Polish–Soviet commission to examine the incident. The Soviet Union then claimed that the Polish response was hostile and severed diplomatic relations with Finland on 28 October. Two days later, Marshal of Poland Edward Rydz-Śmigły announced the mobilization of Polish troops.

Geography
Poland's shared border with the Soviet Union was 1412 km long. By comparison, the border with Germany and its province of East Prussia was more than 20 percent longer, at 1912 km. Neither border contained any major geographical obstacles, making defense very difficult.

In the north there was a flat, plain land with huge forests (e.g. Puszcza Nalibocka — the Wilderness of Naliboki). In addition, a major rail route connecting Moscow to Western Europe extended across the northern portion of the country. The areas major conurbation at the time was Wilno, located in the northeast corner of interbellum Poland.

The centre region of the country was primarily composed of a huge, sparsely populated swamp known as Polesie. This land had no roads and few rail lines. However, it held supreme strategic importance, as its landscape made possible a prolonged, organized defense. Neither Polesie nor the adjacent Volhynia contained any major urban centers.

The south, formerly a portion of the Galicia province of the Austrian Empire, was the most highly developed, with a high density of rail lines, growing industry (e.g., oil fields in Boryslaw), and the well-developed agriculture of Podolia. Lwów, one of the major urban centers of interbellum Poland, was located in this area. In addition, the Soviet border was marked by a natural obstacle — the Zbrucz river.

Virtually all Polish industrial and urban centers were located in the West. This made long-lasting defense possible, as a Soviet force would have taken up to several weeks to reach Upper Silesia, Warsaw, Kraków or Poznań. While devising Plan Wschód, Polish planners assumed cooperation and support would be forthcoming from Romania, which was Poland's main ally in the East.

Poland
During the 1920s and 1930s, the leaders of the Republic focused their efforts on countering the potential threat from the East. Fresh were memories of the Polish-Soviet War and the Battle of Warsaw, which saved both Poland and Europe from the spread of Bolshevik revolution by force. Both the Polish Army and the government in Warsaw were certain that war with the Soviets was inevitable, thus preparations for it (known as Plan East, or Plan Wschód) were far more advanced than preparation for armed conflict with Germany (known as Plan West, or Plan Zachod).

The plan, developed between 1935 and 1938 and headed by Lt. Col. Leopold Okulicki, was based on the notions of Józef Piłsudski, who, until his death in 1935, was sure that war would arrive from the East. Thus most army maneuvers and field fortifications built by Polish Corps of Engineers (especially around Sarny) were held in the east, while Poland's western border was, to a large extent, neglected.

Polish planners were well aware that the Red Army was in many elements superior to their own. Therefore, the main idea was to organize a so-called "resistance in motion", and to try to split Soviet forces south and north of the vast Polesie swamps. Front line armies, located in the vicinity of the border, were to try to delay the advance of the aggressors and to bleed them, while reserves, located mostly in the area of Brześć Litweski and Lublin, were intended to enter the conflict in later stages. The Poles were expecting the Red Army to advance in three directions. Firstly, along the Minsk - Baranowicze - Białystok - Warsaw rail line. Secondly, along the Sarny - Kowel - Lublin line, and finally, in the south along the Tarnopol - Lwów line.

The plan predicted that the Soviets would attack north and south of the Pińsk (Pripet) Marshes, the bulk of the Polish Army was supposed to have been concentrated both in the north and south, with central section of the border left mostly unguarded. The Polish forces were mobilized as follows:


 * In the extreme north-east, around the rail nexus of Mołodeczno, was Armia Wilno under the command of Div. Gen. Stefan Dąb-Biernacki. It comprised three infantry divisions (1st Legions Infantry Division from Wilno, 19th Infantry Division, also from Wilno, 29th Infatry Division from Grodno), two cavalry brigades (Wileńska Cavalry Brigade from Wilno, Suwalska Cavalry Brigade from Suwałki), and the 5th Air Corps from Lida.
 * South of Armia Wilno was Armia Baranowicze under the command of Div. Gen. Tadeusz Piskor. It comprised four infantry divisions (9th Infantry Division from Siedlce, 20th Infantry Division from Baranowicze, 18th Infantry Division from Łomża, and 28th Infantry Division from Warszawa), two cavalry brigades (Nowogródzka Cavalry Brigade from Baranowicze, Podlaska Cavalry Brigade from Białystok) and the 4th Air Corps from Toruń.
 * In the center was Independent Operational Group Polesie under the command of Brig. Gen. Emil Krukowicz-Przedrzymirski. It was composed of three infantry divisions (8th Infantry Division from Modlin, 27th Infantry Division from Kowel, 30th Infantry Division from Kobryń), one cavalry brigade (Mazowiecka Cavalry Brigade from Warszawa), the Riverine Flotilla of the Polish Navy and the 3rd Air Corps from Poznań.
 * Further south was Armia Wołyń under the command of Div. Gen. Stanisław Burhardt-Bukacki. It comprised three infantry divisions (2nd Legions Infantry Division from Kielce, 3rd Legions Infantry Division from Zamość, 13th Infantry Division from Równe), one cavalry brigade (Wołyńska Cavalry Brigade from Równe) and the 2nd Air Corps from Kraków.
 * In the extreme south was Armia Podole under the command of Div. Gen. Kazimierz Fabrycy. It comprised five infantry divisions (5th Infantry Division from Lwów, 11th Infantry Division from Stanisławów, 12th Infantry Division from Tarnopol, 22nd Infantry Division from Przemyśl, 24th Infantry Division from Jarosław), two cavalry brigades (Podolska Cavalry Brigade from Stanisławów, Kresowa Cavalry Brigade from Brody) and the 6th Air Corps from Lwów.
 * Apart from these units, in all armies there were Border Protection Corps (Polish: Korpus Ochrony Pogranicza, KOP) units and garrisons of the main cities.

The army had also following reserve forces:


 * Behind Armia Wilno and Armia Baranowicze was Armia Lida, consisting of three infantry divisions.
 * Behind Armia Podole and Armia Wołyń was Armia Lwów, made up of two infantry divisions and a cavalry brigade (5th Krakowska Cavalry Brigade from Kraków).
 * Far behind the front lines, around the city of Brześć Litewski, was the main reserve, which comprised six infantry divisions, two cavalry brigades (7th Wielkopolska Cavalry Brigade from Poznań, 8th Pomorska Cavalry Brigade from Bydgoszcz), an Armored Brigade and the 1st Warsaw Air Corps.

Soviet Union
During the ongoing negotiations between Poland and the Soviet Union, Stalin instructed the Chief of Staff for the Red Army, Marshal Boris Shaposhnikov, to prepare a plan for the invasion of Poland. Shaposhnikov outlined an plan with a duration of several months, which advocated for a serious buildup, extensive logistical and fire support preparations, and a rational order of battle, deploying the army's best units.

The Soviets employed two primary offensive axes, each managed by a Front. Each Front commander had at his disposal a mobile group of forces created from cavalry and mechanised troops; a precursor of the cavalry-mechanised groups of the Second World War.

The Soviet forces, numbering between 450,000 and 1,000,000 soldiers, 2500 tanks and 718 armoured cars and 3800 aircraft, were positioned as follows:
 * North of the Pińsk Marshes, the Belorussian Front was under the command of Komandarm 2nd rank Mikhail Kovalyov.
 * South of the Pińsk Marshes, the Ukrainian Front was under the command of Komandarm 1st rank Semyon Timoshenko.

Stalin's purges had devastated the officer corps of the Red Army; those purged included three of its five marshals, 220 of its 264 division-level commanders or higher, and 36,761 officers of all ranks. Fewer than half of the officers remained in total. They were commonly replaced by soldiers who were less competent but more loyal to their superiors. The effects of the purge are visible in the ranks of the commanders in the order of battle, with only one Army commander serving in the appropriate rank of the Army General, in this case 2nd Class (Komandarm 2nd rank, Russian: командарм 2 ранга), the rest serving in being Corps (Komcor) and Divisional (Komdiv) Commander rank Russian: комкор, комдив). Furthermore, unit commanders were superseded by a political commissar, who ratified military decisions on their political merits, further complicating the Soviet chain of command. This system of dual command destroyed the independence of commanding officers.