Censorship: Censorship of books, newspapers, and other publications was widely practiced to prevent the spread of liberal ideas.
Surveillance: Secret police forces were established to monitor the activities of suspected liberals and to gather intelligence on potential threats to the established order.
Repression: Political opponents were often subject to arrest, imprisonment, or even execution.
Economic sanctions: Economic sanctions were sometimes used to pressure states that tolerated or supported liberalism.
Military intervention: In some cases, military intervention was used to suppress liberal revolutions or to support conservative regimes threatened by liberal movements.
The Concert of Europe, an alliance of the major European powers formed after the Napoleonic Wars, also played a role in preventing the spread of liberalism. The Concert powers pledged to intervene collectively to maintain the status quo and to prevent any one country from becoming too powerful. This effectively prevented liberal revolutions from spreading from one country to another.
Despite these measures, liberalism did eventually triumph in Europe. The revolutions of 1848-1849 led to the establishment of liberal regimes in several countries, and by the end of the 19th century, liberalism had become the dominant ideology in Europe.
