Comrade Stalin, Kremlin, late 1930's
A wiser, kinder, truer, more capable or dedicated public servant has never graced the earth. He had no tolerance for anyone who thought otherwise.
I struggled for a long time to understand the purges. They seemed so deliberately wasteful, employing huge resources to deal with people who represented no real threat to Stalin's power. The answer, I think, was paranoia and ambition.
The first thing is Stalin's paranoia. He started by bumping off his chief rival, Sergei Kirov in 1934. Then he went after the rest of his rivals in the high halls of the party by framing them for Kirov's murder and increasingly wild accusations of conspiracy to overthrow the revolution. Then he had people methodically go through the institutions of the state for their sympathizers and allies. So far so good for a ruthless, paranoid dictator. But it should have stopped there. Instead, there were waves of purges that rippled outward through the entire society. They went on and on for years. In the end, Stalin removed not only his opponents, but anyone who might have the motivation or means to become an opponent sometime in the future. This is why the families of purge victims were often shipped to labor camps in Siberia. Conservative estimates put the minimum number executed at about 1 million. Another 1.5 - 2 million died in the Siberian camps.
The second reason was ambition. He wanted to entirely remake greater Russia in his image. At one point in the late 1930's, he called together all the storytellers and folk singers in the Soviet Union for a grand convention. Then he had them all shot. There would be no memory, no history, no identity not dictated by Stalin.
Eventually, the purges carried off the majority of senior soldiers, politicians, bureaucrats, industrialists, academics, intellectuals and scientists. The purges burned out in 1938 after there was nobody left in the Party, the state institutions or the military who could be suspected. Stalin was triumphant. The survivors were sycophants, or apparatchiks. The disastrous impact of these purges on the Soviet Union's capabilities became stark in the weeks following June 22, 1941.