Geographers are not agreed as to precisely which lands are to be regarded as included in or lying outside Europe. There is a difference of opinion concerning several islands in the Atlantic and the Mediterranean. Here, Great Britain and Ireland; Iceland; the Faeroe, Channel, and Frisian Islands; Madeira and Heligoland; Cyprus, the Ionian, Balearic, and Aegean Islands; Corsica and Sardinia, Sicily, Malta, and Crete will all be included as part of “Europe.”

There are also difficulties in classifying the Ottoman Empire and Russia, which, in terms of their histories and geographical location, straddle two regions.

Some or all of both entities should be considered as part of Europe. Russia actively participated in the Napoleonic Wars that were fought during the period with which this study begins. After 1815, Russia played a major political role in Europe. Russia, together with Great Britain, Austria, and Prussia, formed a Quadruple Alliance that provided for collective security against a renewal of French aggression and a “Concert of Europe” to facilitate major power cooperation in keeping order. Russia, with its “Army of Europe,” and Austria led the Concert in intervening to put down uprisings in Spain and Italy (1820s), in Poland (1830), in Hungary (1848–49), and in Herzegovina (1862). The Ottoman Empire was also intimately involved in the affairs of Europe. It was weighed in the balance of Europe throughout the nineteenth and early twentieth centuries.