Nearly two years after the start of World War II, Nazi Germany launched Operation Barbarossa, an invasion of the Soviet Union. It was one of the largest and deadliest conflicts of all time, and it wasn't until the 1960s that the Soviet Union recovered economically. It is estimated that more than twenty million Russians were killed in the invasion. Overall, the Soviet Union suffered more losses than any other country involved in World War II. Before the war broke out, Soviet leader Stalin was cooperating with the German army. World War I did not end amicably for the Germans, and many were unhappy with the outcome. Stalin allowed the German armed forces to train secretly in the Soviet Union because the Treaty of Versailles imposed restrictions on German military. In return, Germany supplied Stalin with machine parts and other goods. Despite being a staunch anti-communist, when Hitler came to power, he continued to exploit this trade-off. Stalin knew that war with Germany was inevitable, as Hitler declared in his manifesto, Mein Kampf. But he wanted to direct Germany's attention to France and Britain, giving him more time to strengthen his army.
In 1936, Hitler began to rebuild power in Germany. He annexed Austria and took over Czechoslovakia, manipulating French and British concessions in the name of peace. The Nazis then allied themselves with Hungary, Romania, Italy, and Japan. When Stalin realized what was happening, he found himself surrounded by German allies. Because France and Britain were reluctant to declare war, he had to negotiate with Hitler. Behind the declaration of trade agreements and the assurance of non-war, Hitler secretly agreed not to interfere if Stalin attacked Finland, and gave Stalin the freedom to rule to take over parts of the Baltic states and Romania. They then distributed Poland to them, which they thought made sense because Poland had been under prussia and Soviet control until it gained independence after World War I. While Stalin seemed to have a better ending from the deal, what Hitler wanted was a guarantee that the Soviet Union would allow Germany to wage war against France. In September 1939, Hitler and Stalin attacked Poland from opposite sides, and their armies met on the agreed stop line to congratulate each other. Shortly after the battle, Stalin's army attacked Finland. Russia won the victory, and the Finns had to cede part of the territory. In 1937, Mikhail Tukhachevsky, a popular Soviet military chief who wanted to modernize his army, was killed. Some believe that Stalin saw Tukhachevsky as a rival, which led him to clear the army of anyone suspected of anti-communist or anti-Stalin sentiments. Thirty-seven thousand officers were either killed, sent to Siberian labor camps, or imprisoned. Marshals, admirals, and admirals were executed, and about ninety percent of corps commanders and eighty-two percent of division generals were executed. In addition to these upper echelons, Stalin also replaced some colonels, majors and captains.
Stalin believed that well-trained commanders were not needed, because the "revolutionary enthusiasm" was enough for them to win. By the time the Soviets went to war with Finland, most of the officers in the army were afraid to disobey orders and think for themselves. The zeal of the revolution meant that the only strategy they could use was to send wave after wave of people to die. Despite being outnumbered, the Finns dragged the Soviets for two months. After heavy casualties, Stalin reorganized, adopted different tactics, and resumed the offensive, and in February 1940, the Finns negotiated the Moscow Peace Treaty. The Soviet Union's military incompetence during the Winter War with Finland prompted Hitler to begin Operation Barbarossa. He hopes to achieve victory as soon as possible to avoid the harsh winter in Russia. However, he greatly underestimated the industry and size of the Soviet army. The Germans assembled the largest invading force in history, complemented by formations from Finland, Italy, Romania and Hungary. Both sides possessed a large number of weapons, including tanks and heavy artillery. Although German tanks were inferior to many Allied tanks, German training and tactics won them victories in the first two years of World War II. The Germans overwhelmed the enemy by finding weaknesses, and then, with the support of air raids, sent tanks through the enemy's front lines. The attackers continued to advance to the rear, where supplies and communications were cut off. German infantry would then follow and destroy any unit still on the front line, a maneuver known as blitzkrieg. Many, including Winston Churchill, warned Stalin of Hitler's intentions to invade, but he chose to ignore them. The German reconnaissance planes were not challenged, and Stalin did not want to provoke an incident unnecessarily. He believed that the Soviets were unprepared for a conflict with Germany and wanted to stop it for as long as possible. Fortunately for the Soviets, later that year, Stalin would listen to some intelligence from one of his agents in Tokyo. The news was that Japan intended to go to war with the United States rather than the Soviet Union, which prompted Stalin to move large numbers of militias from the east to Moscow.
Shortly after 3 a.m. on June 22, 1941, 3 million Germans and their allies crossed the borders of Poland, the Baltic States, Ukraine, and Finland. The Soviets were completely unprepared for the attack, and large numbers of Soviets were surrounded before they realized what was happening. In the first battle, nearly half a million Soviet soldiers were killed. Stalin, ashamed not to believe that Germany would attack, did not speak publicly until more than a week after the first invasion. Hitler wanted to eliminate communism, which promoted the unity of the working class regardless of race, and the Soviet people themselves. There were about 5 million Jews in the Soviet Union, who, along with other Slavic peoples, were starved to death or worked to death by the Germans. As soon as German troops entered the Soviet army, the SS and other police forces began rounding up anyone deemed a threat to the Nazis. The German army advanced forward, broke through the weak points, and then joined the other German troops into the rear of the Soviet forces, separating parts of the Red Army from each other. Since Stalin's purges of disobedient officers are still fresh in their minds, Red Army commanders were hesitant to act on their own. Coordination was not possible because the Germans cut off communications. Within weeks, the Germans had advanced hundreds of miles into the Soviet Union. Panic spread and civilians tried to flee, but they found themselves surrounded and attacked by bombs from the Luftwaffe. Surprisingly, the Germans were not always seen as an invading force. In Ukraine, they were popular liberators oppressed by Stalin, and although there were many Ukrainians who fought against them, civilians often encountered German soldiers with traditional gifts and garlands. The reception, combined with the success of the Blitzkrieg, prompted the Nazis to believe that victory was in their hands, but that the cold Russian winter was upon them.
When the Nazis' true genocidal intentions became clear, any friendliness they showed to the Nazis upon arrival quickly disappeared. Organized resistance begins to grow and will continue into the second year. The Germans did not plan a protracted war, and going deep into Soviet territory, their supplies began to run out. They also suffered many casualties, and while the Soviets had excess manpower, the Germans did not. As the weather deteriorated, the strength of the Soviet army began to show. Stalin was already aware of the negative impact of his management on the armed forces and gave his generals more control. He allowed field commanders to decide how to organize their forces and when to attack or retreat. In late November, the Eastern Reserve Reinforcements arrived, and the Soviets began a modern training system. They mastered the tactics the Germans used against them. Britain and the United States, aware of Russia's nazi control, began providing substantial military assistance, including weapons, food and factory parts. Before Operation Barbarossa began, the Germans had to invade Greece due to the failure of the Italian offensive, which delayed the operation for six weeks. Some argue that the six-week delay doomed them from the start, as it meant the Germans knew they had arrived in Moscow in the winter of 1941. It was also believed that if Hitler managed to occupy Moscow, it would not affect the Soviets, since they had already accomplished the extraordinary feat of transferring most of their important factories to the Ural Mountains, which were out of reach by German bombers.
In the summer of 1941, millions of Soviet soldiers were captured; some were held in unhygienic conditions, leaving them to die of exposure, starvation or disease. Hundreds of thousands of people were shot or sent to German-controlled countries to work in or die in labor camps, and Soviet prisoners of war were the first to use poison gas at Auschwitz. Even more tragically, those who survived the horrors of the war and returned home were suspected by Stalin of being spies or traitors and sent to Soviet camps. The Germans were amazed at their success, killing or capturing so many Soviet troops that they were convinced that the Russians could not hold on. But as autumn approached, Soviet troops kept arriving, and they became more and more assertive. Fighting continued near Kiev from late August to early September 1941. The Soviets initially had about 600,000 troops in the area, with more arriving throughout September. The Germans began to lose their optimism, and many soldiers grew weary of the endless Soviet plains. Their hopes of early victory were dashed, and the Soviets continued to confront them head-on and lead them deep into the desolate lands. As they advanced, the Nazis committed many atrocities, such as the murder of more than thirty thousand Jews in Babiar. Since the end of World War II, thousands of execution sites have been found across Ukraine. After the First Battle of Kiev, Hitler moved most of his army north to Moscow, but by then winter had arrived. The siege lasted from October to January 1942, and the Germans could only see the kremlin's spire. Encouraged by the summer victory, they moved on, but now the German soldiers found themselves without winter coats, in sub-zero temperatures and in short supply. Machines and tanks had to keep running to prevent them from freezing, but that didn't help the situation. Frostbite incapacitated many German soldiers and sometimes even killed them.
On December 5, with german morale low, the Soviets attacked from the frozen fog. The Soviets managed to repel the Germans for hundreds of miles, and while the Germans did stabilize the front, their hopes of conquering Moscow had been dashed. Operation Barbarossa was technically successful, but even Hitler admitted that he grossly underestimated the Soviets. His early victories reinforced his conviction that he would easily defeat the Reds, but while they suffered losses, the Reds were learning and improving their skills. They replaced incompetent officers and newly appointed commanders gained more freedom of movement. It was these commanders who led the Red Army into Berlin in 1945.