An observer of international politics in the 1860s with liberal sympathies could not fail to be disturbed about the apparent coincidence of two facts. The preceding half-century had constituted one of the longest periods of peace in European history, punctured only by occasional and limited military conflict in the margins. The long calm had created conditions for an unprecedented economic growth whose fruit may have been unevenly distributed but seemed tangible enough as proof that European civilization had been launched on an irreversible march towards economic and spiritual progress.

On the other hand, peace had been created and enforced through a pact among five Great Powers, three of which (Austria, Prussia, and Russia) were governed by absolutist monarchs whose main motive for co-operation seemed to be their shared wish to curb any proposal for representative government or increased franchise.