Complete the following sentence: The Soviet Union invaded Poland in September 1939 under the Molotov<unk>Ribbentrop Pact with Germany; the Soviet Union invaded Poland in September 1939 under the Molotov<unk>Ribbentrop Pact with Germany; the Soviet Union invaded Poland in September 1939 under the Molotov<unk>Ribbentrop Pact with Germany; the Soviet Union invaded Poland in September 1939 under the Molotov<unk>Ribbentrop Pact with Germany; the Soviet Union invaded Poland in September 1939 under the Molotov<unk>Ribbentrop Pact with Germany; the Soviet Union invaded Poland in September 1939 under the Molotov<unk>Ribbentrop Pact with Germany; the Soviet Union invaded Poland in September 1939 under the Molotov<unk>Ribbentrop Pact with Germany; the Soviet Union invaded Poland in September 1939
️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️ Although the USSR had outstanding scientists and engineers, began research on what would later become radar ("radiolokatsiya", lit. radiolocation) as soon as anyone else, and made good progress with early magnetron development, it entered the war without a fielded, fully capable radar system.