[5] In the second attempt, Keller received multiple shrapnel wounds, when a bomb exploded beneath his horse.

[8] During the offensive at the end of April 1915, he distinguished himself with a successful cavalry attack at Balamutivka and Rzhavyntsi, breaking through Austrian fortifications, taking strategically important heights and many prisoners.

[9] After the February Revolution in 1917, Keller was one of the two Russian generals, along with Huseyn Khan Nakhchivanski, who supported the Tsar.

[10] Count Keller refused to take the oath of allegiance to the Russian Provisional Government, and was dismissed from his position.

[3] Later Keller moved to Kiev, where on 19 November 1918 he was appointed by hetman Pavlo Skoropadskyi the commander-in-chief of all the troops on the territory of Ukraine.

Skoropadskyi needed the support of Russian monarchists in his struggle against the Ukrainian insurgents, but Keller understood the appointment as the beginning of his own dictatorship.

[11] Skoropadskyi dismissed Keller on 26 November for "overstepping his authorities" and replaced him with general Prince Alexander Dolgorukov.