Introduction:
After the defeat of Napoleon Bonaparte in 1815, the Congress of Vienna established a conservative order in Europe which aimed to suppress the revolutionary ideas that had spread during the French Revolution. However, despite the conservative efforts, the revolutionary ideologies continued to spread in many European states.

1. Intellectual Circles:
Revolutionary ideas were often disseminated through intellectual circles, where like-minded individuals gathered to discuss and promote their ideologies. These circles included writers, philosophers, and academics who shared their ideas through books, pamphlets, and journals. For example, Karl Marx and Friedrich Engels published "The Communist Manifesto" in 1848, which outlined their revolutionary ideas and influenced many across Europe.

2. Nationalism:
Nationalism played a significant role in the spread of revolutionary ideologies. The idea of a nation-state, where people of a common nationality would have their independent state, appealed to many Europeans. Nationalist movements emerged in various countries, advocating for self-determination and independence from imperial powers. For instance, Giuseppe Mazzini, an Italian nationalist, founded Young Italy in 1831 to promote the unification and independence of Italy.

3. Secret Societies and Underground Movements:
Revolutionaries also formed secret societies and underground movements to spread their ideologies and organize resistance against the conservative regimes. These clandestine groups operated covertly, often using encrypted communication and conspiracy to avoid detection. The Carbonari, a secret society founded in Italy in the early 19th century, aimed to overthrow foreign rule and establish a democratic republic.

4. Revolutions and Uprisings:
Revolutionary ideologies gained momentum through actual revolutions and uprisings across Europe. Events like the July Revolution of 1830 in France and the Revolutions of 1848 in multiple European states provided opportunities for revolutionaries to mobilize the masses and advocate for their ideas. The 1848 Revolution in France led to the establishment of the Second Republic and inspired revolutionary movements in other countries as well.

Conclusion:
Despite the efforts of conservative forces to suppress revolutionary ideologies, they continued to spread in Europe through intellectual circles, nationalism, secret societies, and actual revolutions. These ideas played a crucial role in shaping the political landscape of Europe in the 19th century, leading to the rise of liberalism, socialism, and nationalist movements.