Queen Isabella II of Spain (1830–1904) was a central figure in Spanish history during the mid-19th century. In 1851, she was in the early years of her controversial reign, which began when she was a child. Her monarchy was marked by political instability, factionalism, and challenges to her legitimacy.

The Provisional Government of Spain in 1870 was a transitional regime established during one of the most turbulent periods in Spanish history. This government was part of the broader political reorganization following the Glorious Revolution of 1868, which had deposed Queen Isabella II and sought to create a more liberal and democratic system in Spain.

King Amadeo I of Spain (1845–1890) was an Italian prince who reigned as the King of Spain from 1870 to 1873. His brief tenure marked a period of significant political turmoil and transformation in Spain.

King Leopold II of Belgium, who reigned from 1865 to 1909, is often remembered for his role in colonizing the Congo Free State.

King Alfonso XII of Spain (1857–1885) was a key figure in Spanish history, remembered for his role in restoring the Bourbon monarchy during a turbulent period of political instability.

William I of Prussia (1797–1888), later Emperor William I of Germany, played a pivotal role in the unification of Germany and the establishment of the German Empire.

King Alfonso XII of Spain (1857–1885) was a key figure in Spanish history. During his reign a new constitution was promulgated, establishing a constitutional monarchy with a parliamentary system.

King Alfonso XII of Spain (1857–1885) was a key figure in Spanish history. During his reign Alfonso played a significant role in ending the Third Carlist War (1872–1876), a conflict with Carlist factions seeking to place a rival branch of the Bourbon family on the throne.

The Meiji Era (1868–1912) was a transformative period in Japanese history, marked by rapid modernization, industrialization, and the reorganization of Japan's political, economic, and social structures.