Career
He was also known as "the patriarch of the Bulgarian military". Danail Nikolaev was born in Bolgrad, Russian Empire (now Ukraine) to a Bulgarian family, who were refugees from Tarnovo. In 1871 he graduated from the Bolgrad Gymnasium and joined the Volunteer company of 54th Minsk regiment.
On 19 September 1873 he joined the Infantry school in Odessa as a cadet, graduating in 1875.
Nikolaev returned to his regiment in Chişinău as an acting cadet on 20 July. Realizing that Serbia was preparing for war with the Ottoman empire, he requested resignation from military service to join the war on 14 June 1876.
His request was reviewed by division commander General Dragomirov, who furloughed him instead. As a volunteer he took part in Serbo-Turkish War in the battles of Babina glava, Mirovitsa and Gamzi graduate