It used to be that brutal violence was the weapon the ruling class used against the peasants, serfs and slaves to keep them down, but in the last 1,000 years this has changed. In this time, all over Europe, there has been many peasant uprising, most of which were brutally put down. The two largest was the Wat Tyler's Rebellion of 1381 in England that nearly succeeded and the German Peasant's war of 1524–1525.
The first successful rebellion against the ruling class was the English civil war of 1642–1651, which resulted in the King Charles 1 being beheaded. Unfortunately his place was taken by a brutal dictator called Oliver Cromwell who although was a brilliant general, was also a despotic ruler. He ruled the country so badly that after he died, the son of King Charles 1, Charles 2 was invited back to rule Britain. But he wasn't allowed to rule as an absolute monarch like his father and parliament has since became more and more powerful.
The next two successful revolutions was the American War of Independence, 1775–83 and the French Revolution of 1789–1799. In the French Revolution not only did they behead their King, they also executed a very large number of the elite ruling class as well. What these revolutions established, was that the ruling elite could no longer depend on violence and intimation to keep the people down. This was because the people realised that successful revolution against the ruling elite was possible. Because of this, in the 19th and 20th centuries there have been many revolutions all over the world. So the ruling elite have had to use other methods like propaganda and high unemployment, to keep the workers down.
The use of high unemployment was successfully used in the 1930s, where a financial crash was engineered in 1929, causing a world wide depression. As the media is controlled by rich and powerful men, they sold to the people the story that the depression had nothing to do with the ruling elite, it was caused by an unforeseen stock market crash. And the people didn't question this, because no-one in the media was saying anything different.
Unemployment is a very powerful tool to use against the working class and even the middle class. This is because, in times of full employment, workers have a choice about whom they can work for. So if a boss is not paying very high wages or is treating his workers badly, they are free to leave and work for someone else who pays better wages and treats his workers better. As the result, full employment gives workers more power, resulting in better wages and conditions.
The opposite is true in times of high unemployment. In these times, if a worker is dissatisfied with his wages or they don't like the way his boss is treating him, then it is more difficult for him to leave, as it is far harder for him to find another job. The result is that full employment gives the workers far more power but high unemployment gives the bosses all the advantages.
So the depression of the 1930s was a good time for bosses as they could drive down wages and exploit their workers but this was to have unforeseen consequences. Russia had a communist revolution in 1917 and was now looking to export their revolution to other countries. So any country where there were disgruntled workers was a fertile place to have another communist revolution. One of these places was Germany.
After the defeat of Germany in the 1914-18 war, the Allies try to make Germany pay for cost of the war to them. This bankrupted Germany and so when the depression started the German workers suffered more than most other countries. This resulted in the communist party in Germany becoming very powerful. To prevent a communist revolution in German, very wealthy people in USA, financed a national socialist party which we now call the Nazis. As the result they just managed to win an election and once its leader, Adopt Hitler, got into power he ruled as a dictator. Unfortunately the Nazis wanted to settle old scores and set about conquering Europe, which resulted in the Second World War. The capitalist countries soon recognized that the Nazis were a greater threat than the communist. As a result, found themselves allied to communist USSR in defeating Nazi Germany.
The communist USSR done well out of the Second World War and was able to take over countries like Poland, East Germany, Czechoslovakia, Hungry, Romania and Bulgaria. What is more, in 1949, China had a communist revolution and like Russia was keen to export communism to the rest of the world. This was to result in the Korean war and later the Vietnam war, as the USA tried to prevent more countries becoming communist.
With the world wide threat of communism, it became clear that Western countries couldn't afford to have disgruntled workers, if they didn't want to have any more communist revolutions. As the result, they had to engineer the economy so there was full employment. This gave the workers far more power then they ever had before. During the time of the cold war in the 1950s, 60s and 70s the gap between rich and poor was steadily decreasing, as the worker were able to demand better and better wages and working conditions. The rich off course didn't like this, but put up with this, as they still feared communism. But then in the 1970s it became clear that the USSR was losing the cold war. While with the death of the Chinese dictator Mao Tse tung in 1976, the new Chinese communist leaders began to accept capitalist ideas.
Even though the Soviet Union spending half of its resources on military spending, it was still losing the technology battle and could no longer keep up with the west in producing new sophisticated weapon systems. So with the communist no longer seen as a threat, the ruling elite could engineer a new depression. Though it wasn't so bad as the depression in the 1930s and they called it a recession instead. As the result in the 1980s we had high unemployment, which destroyed the power of the unions and working class people. Then because of this, the gap between rich and poor has been growing ever since. The result was that all the benefits of new technology like commuters and robotics didn't go to the working class, but to the rich and powerful.
In spite of all the benefits gained for the rich by years of high unemployment the rich still don't think they have a sufficient amount. After all, perhaps being a billionaire is not enough, why not become a multibillionaire instead? So in 2008 another financial crises was engineered, so the rich could raid the worker's pension funds and cut social security and drive down wages even more. After all, unemployment pay, and social security has always been seen as a problem to many rich people. It would be better if all these things were done away with, so if a person loses his or her job, they would stave to death in the streets. Like what used to happen in the 'good old days' in the 19th century. This would give the bosses enormous power over the workers.
Nowadays there is nothing to stop the rich and powerful doing this. There is no longer a communist threat, and rich people control the media, so they believe there is little chance of revolution. Unfortunately the rich will keep on trying to exploit the poor until the workers and perhaps the middle class can organize themselves to start a new revolution.