Well the early 1800s included the Napoleonic Wars - which was bloodier than many of the earlier wars against France - while the latter half had the wars of German unification and the Crimean War. And that doesn't count the numerous liberal revolutions that occurred throughout Europe particularly the Paris Commune.

My impression is that it was not necessarily a much more peaceful century; but it seems that way because of the British insistence on the "Pax Britannica" narrative after the Congress of Vienna.

Beginning with Haiti and continuing through the vast majority on the Latin American countries, most areas of the Western hemisphere were fighting for independence in the early part of the 19th century. For most countries seeking independence from Spain, this process lasted about twenty years. A large part of the hemisphere was submerged in warfare for a fifth of the century, and that does not take into account the Civil War in the U.S., the Mexican American War, the War of the Pacific, the Spanish-American War, and the Franco-American Wars. Considering the whole of the hemisphere, I would say that the 1700s were more peaceful.

Edit: cleaned up grammar

Nicholas Boyle, author of a multi-volume Goethe biography, thinks so:

Prof Boyle argues that 2014 will be important because previous five centuries have also hinged on events that took place in the middle of their second decade.

In 1517 Martin Luther nailed his theses to the door of Wittenburg church, sparking the Reformation and the rise of Protestantism.

A century later 1618 marked the start of the 30 Years War and decades of religious conflict in Western Europe, which ended with the establishment of the Hanoverians in 1715.

The enlightened Congress of Vienna took place in 1815 following the defeat of Napoleon, heralding a century of relative stability across Europe.

But in 1914 the First World War broke out, a catastrophic conflict that would claim millions of lives and set the tone for international discord throughout the 21st century.