Final answer:
Conservatism was challenged after 1815 by liberalism, nationalism, and socialism.
Step-by-step explanation:
After 1815, conservatism faced challenges in Europe primarily from liberalism and nationalism. The revolutions of 1848 shook Europe but ultimately conservative monarchs regained control. However, conservatism itself gradually adopted liberal and nationalist traits, leading to the conservative-led national unifications of Italy and Germany. Socialism emerged as a new political movement that opposed conservatives, liberals, and nationalists.