When Stalin was told about it, he answered: "If there is no ill will, they [the soldiers] can be pardoned". In one notorious massacre, the NKVD-the Soviet secret police—systematically executed 21,768 Poles, among them 14,471 former Polish officers, including political leaders, government officials, and intellectuals. Some 4,254 of these were uncovered in mass graves in Katyn Forest by the Nazis in 1943, who then invited an international group of neutral representatives and doctors to study the corpses and confirm Soviet guilt, but the findings from the study were denounced by the Allies as "Nazi propaganda". The Soviet Union had ceased to recognize the Polish state at the start of the invasion. As a result, the two governments never officially declared war on each other. The Soviets therefore did not classify Polish military prisoners as prisoners of war but as rebels against the new legal government of Western Ukraine and Western Byelorussia. The Soviets killed tens of thousands of Polish prisoners of war. Some, like General Józef Olszyna-Wilczyński, who was captured, interrogated and shot on 22 September, were executed during the campaign itself. On 24 September, the Soviets killed 42 staff and patients of a Polish military hospital in the village of Grabowiec, near Zamość. The Soviets also executed all the Polish officers they captured after the Battle of Szack, on 28 September. Over 20,000 Polish military personnel and civilians perished in the Katyn massacre. The Poles and the Soviets re-established diplomatic relations in 1941, following the Sikorski-Mayski Agreement; but the Soviets broke them off again in 1943 after the Polish government demanded an independent examination of the recently discovered Katyn burial pits. The Soviets then lobbied the Western Allies to recognize the pro-Soviet Polish puppet government of Wanda Wasilewska in Moscow. On 28 September 1939, the Soviet Union and Germany had changed the secret terms of the Molotov–Ribbentrop Pact. They moved Lithuania into the Soviet sphere of influence and shifted the border in Poland to the east, giving Germany more territory. By this arrangement, often described as a fourth partition of Poland, the Soviet Union secured almost all Polish territory east of the line of the rivers Pisa, Narew, Western Bug and San. This amounted to about 200,000 square kilometres of land, inhabited by 13.5 million Polish citizens. The Red Army had originally sowed confusion among the locals by claiming that they were arriving to save Poland from the Nazis.