When the future emperor Alexander II of Russia, as tsarevich, chose the sixteen-year-old Marie as consort, his parents consented to the match as worthy due to the Grand Duke's acknowledgement of her as his daughter.

Because of her youth, Alexander escorted his sister to Russia for her wedding, remaining at the Russian court and joining the inner circle of his brother-in-law the tsarevich after the rest of Marie's entourage returned to Hesse.

Alexander fell in love with Countess Julia von Hauke, lady-in-waiting to his sister (known, since her conversion to Orthodoxy, as Maria Alexandrovna, ranking only after her mother-in-law the Empress Alexandra Feodorovna).

Alexander left for England to contemplate his future, but then returned to Russia and eloped with Julia from St. Petersburg, being stricken by the Emperor's orders from the roll of the Russian imperial army for insubordination.

Grand Duke Louis III therefore chose to distinguish her from several non-royal wives of other Hessian princes by conferring upon her, along with the Battenberg countship, the style of Erlaucht (Illustrious Highness), usually reserved in Germany for counts of mediatized (i.e., dynastic) rank.

As a cadet of the Hessian grand ducal dynasty, Prince Alexander had followed the martial tradition of his family by offering his sword to the military service of a Great Power while still a teenager, having accompanied his sister to St. Petersburg.

Although the electorate of Hesse-Kassel, ruled by another branch of Alexander's family, was annexed by Prussia for adhering to the losing side, the fact that Hesse-Darmstadt's grand duke was the brother-in-law of the Russian tsar saved its independence, although not without loss of territory.

In 1858, Grand Duke Louis III raised his sister-in-law from "Countess" to "Princess" (Prinzessin) von Battenberg; her children sharing in the princely title, and accorded them the style of Serene Highness (Durchlaucht).