In mid-19th century, on the eve of the battle of Custoza, which was to lead to a seven-week war between the Austrian Empire, Prussia and their allies, Europe was in turmoil. With the rise of nationalism and territorial aspirations of individual nations, the economic rise of Prussia, and the uncertain political situation in Central Europe, armed confrontation was looming on the horizon. Following the Italian unification and after the appointment of the new Prussian prime minister Otto von Bismarck, who failed to hide his strong anti-Austrian sentiment, the war with Prussia was inevitable.

Reference code: Archives of the Republic of Slovenia, SI AS 1069/VIII/10-13

On account of some rather unwise political decisions, two new fronts were opened for the Austrians; one in Bohemia and the other in Italy. On June 23, the imperial army marched toward Custoza, where on June 24 around three in the morning the two opposing armies engaged in a fierce battle. Among the Austrian troops there was also the 17th imperial-royal infantry regiment, consisting mostly of Slovenians and fighting on the far right wing of the battle line as part of the reserve infantry division under the command of baron Ruprecht. The aftermath of the battle was almost 14 000 soldiers lost on both sides, dead, wounded or captured. Among Slovenians, the battle of Custoza and the Austro-Prussian war in general inspired a number of folk songs, describing the power of firearms, death, and the emperor.

Custoza and other military victories won by the Austrians on the Italian battlefields did not carry much weight in the general scope of the Austro-Prussian war. Their Italian campaign ended on July 21 with the battle of Bezzecca. Irrational courage shown by the Austrian infantry had a frightening effect on the Italian army but less so on the Prussians, whose superior firearms mercilessly decimated Austrian infantrymen. The devastating defeat of the Austrians in Koniggrätz on July 1866 forced the archduke Albert to return back north and the fate of Veneto was decided by means of the Vienna peace treaty. It came under the French rule, but was, due to the will of the people, immediately afterwards given to Italy.

The war delivered a heavy blow to the Austrian Empire. The following year, Hungary forced the establishment of the Dual Monarchy; the new arrangement added fuel to the burning "cage of nations" that finally met its end after World War I.