 Strike action, also called labor strike, labor strike, or simply strike, is a work stoppage caused by the mass refusal of employees to work. A strike usually takes place in response to employee grievances. Strikes became common during the Industrial Revolution, when mass labor became important in factories and mines. In most countries, strike actions were quickly made illegal, as factory owners had far more power than workers. Most Western countries partially legalized striking in the late 19th or early 20th centuries. Strikes are sometimes used to pressure governments to change policies. Occasionally, strikes destabilized the rule of a particular political party or ruler. In such cases, strikes are often part of a broader social movement taking the form of a campaign of civil resistance. Notable examples are the 1980 Grdansk shipyard or 1981 warning strike, led by Lekwalansa. These strikes were significant in the long campaign of civil resistance for political change in Poland, and were an important mobilizing effort that contributed to the fall of the Iron Curtain and the end of Communist Party rule in Eastern Europe.