On this day, 85 years ago, April 3, 1940 (February 26, 1940 in the lunar calendar), Katyn Massacre: The cause and effect of the execution of 21857 Polish officers by the Soviet Union. The "Katyn Incident" is also known as the "Katyn Massacre" and the "Katyn Forest Massacre". On April 3, 1940, approximately 22,000 Polish soldiers, intellectuals, politicians and public officials were killed in the Katyn Forest. It is an eternal pain in the hearts of Poles and has also long troubled relations between Poland and Russia. The Katyn Massacre was an organized massacre carried out by the Soviet secret police of captured Polish prisoners of war, intellectuals, police officers and other civil servants from April 3 to May 19, 1940. About 22,000 Polish soldiers, intellectuals, politicians and public officials in custody were killed. But there were historical reasons for the Katyn tragedy. After World War I, Poland obtained the Polish Corridor, which originally belonged to Germany, dividing Germany and East Prussia in two; in order for Poland to have a coastline on the Baltic Sea, the port of Danzig became a free city with Poland's main rights. Therefore, Poland and Germany have territorial conflicts. In the early days of the Soviet-Polish War, after the Polish army defeated the Red Army, they looted residents, burned all villages, and shot and hanged innocent people in the occupied areas of Ukraine. Captured Red Army soldiers were tortured and insulted. In the city of Novna alone, Polish occupation forces shot dead more than 3000 civilians. The Polish army that won the Soviet and Polish War in 1920. Through the Soviet-Polish War, Poland gained disputed territories of Western Ukraine and Western Belarus from the Soviet Union. As a result, Poland and the Soviet Union were in conflict. In the 1920 Soviet-Polish War, the Polish army used pro-Soviet elements to practice sword skills. A large number of Soviet Red Army prisoners of war died abnormally during the Soviet-Polish War. Due to the historical conflict of the 1920 Soviet-Polish War, Stalin has always been bitter about Poland's blood debt. In March 1938, Germany violated the Treaty of Versailles and annexed Austria. Poland followed Germany's example and issued an ultimatum on the border of Lithuania, demanding that it recognize Vilno as Polish ownership within 48 hours. The Lithuania government was forced to agree. In October 1938, Germany proposed a "general solution" to Poland, requiring Poland to transfer the Free City of Danzig to Germany; at the same time, Germany had the right to build roads and railways connecting Germany with East Prussia through the Polish Corridor;... In return, Germany will guarantee Poland's existing borders. Poland flatly rejected the request. The picture shows Polish troops heading to the front line. On April 11, 1939, Hitler approved the war plan against Poland, code-named "Plan White", and decided to use "Blitz" to defeat Poland in one fell swoop. In the early morning of September 1, 1939, Nazi Germany launched a Blitz against Poland and occupied western Poland. On September 1, 1939, German armored troops entered Poland. Previously, on August 23, the "Soviet-German Non-Aggression Treaty" was signed in Moscow, with a secret supplementary agreement that was not announced to the public, stipulating: "Once territorial and political changes occur in areas belonging to the Polish state, the sphere of influence of Germany and the Soviet Union will be generally bounded by the Pisa, Naref, Vistula and San rivers." German troops entered Warsaw, the capital of Poland. The Polish army suffered heavy losses and retreated towards eastern Poland. On September 17, 1939, the Soviet government declared its obligation to send troops to protect Ukraine and Belarusians in Poland. On the same day, Soviet troops entered Poland from the east and occupied all Polish territory east of the Curzon Line. German and Soviet troops joined forces in Brest, then central Poland. Under the agreement of the Soviet-German Non-Aggression Treaty, Polish territory was divided from the east and west sides. In order to eliminate this potential force that Poland might support the enemy, Polish prisoner of war camp officials gave Stalin a very tempting idea-execution. Beria (second from right) is with Stalin. On March 5, 1940, Beria wrote a report on the execution of more than 20,000 prisoners of war and prisoners, mainly Polish officers. The execution order that determined the fate of 22000 Polish officers was formally approved at the 18th Politburo meeting of the Communist Party of the Soviet Union on May 5, 1940, namely "Question No. 144 of the NKVD". From April 3 to May 19, 1940, General Beria implemented "Question No. 144 of the NKVD". Soviet executioners stood behind the Polish prisoners of war and fired pistols in the back of their heads. After burying the Polish prisoners of war, Soviet personnel laid a thick layer of soil on them. Soon, a second batch of prisoners of war was transported to the area and treated in the same way. Between April 3 and May 19, 1940, General Beria's secret police systematically executed approximately 22000 Polish officers in the western provinces of Belarus and Ukraine and other Soviet-occupied areas (the majority of those executed were Polish officers or government employees captured in 1939). The victims of the Katyn massacre "Resolution No. 144 of the Ministry of the Interior" was one of General Beria's most successful operations, and the process was secretive and without incident. After the outbreak of the Soviet-German War in 1941, the German army occupied the Katyn Forest, where the tragedy occurred. In 1943, Germany accidentally discovered and exposed the Katyn Forest tragedy during construction, which deteriorated relations between the Soviet Union and the Polish government-in-exile at that time in London, England. A German commission of inquiry interviewed witnesses to the Katyn Forest massacre, but the Soviet government never admitted the act and claimed it was caused by the German Nazis. Germany investigated the bullet holes in the bodies of the victims and found that the bullet holes had distinctive characteristics-they came from the secret police unit of the Soviet Army's Ministry of Internal Affairs. According to incomplete statistics, the people massacred in Katyn included a admiral, 2 army generals, 24 army colonels, 79 army lieutenants, 258 army majors, 654 army captains, 17 navy captains, 3,420 non-commissioned officers, 7 chaplains, 3 landowners, 1 prince, 43 officials, 85 soldiers, and 131 refugees. In addition, 20 university professors were among the victims. Half a century later, on January 22, 1991, the Russian government officially admitted to the Polish ambassador that General Beria, leader of the secret police force of the Ministry of Internal Affairs of the Soviet Union, was responsible for the massacre. For hundreds of years, Russia and Poland were both Slavic brothers, and there were many scenes of unclear grudges and feud between them. On April 10, 2010, the Polish President flew a Russian-built plane to attend the "" Memorial Ceremony. He crashed on Russian soil, which undoubtedly added a new chapter to the feud between the two Slavic nations that has been unclear for hundreds of years.