He was the first person to attain the highest rank in the Bulgarian military, General of the infantry.

Danail Nikolaev was born in Bolgrad, Russian Empire (now Ukraine) to a Bulgarian family, who were refugees from Tarnovo.

[1] In 1871 he graduated from the Bolgrad Gymnasium and joined the Volunteer company of 54th Minsk regiment.

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 grad.