[2] In 1880, he began his military service by voluntarily joining the Imperial Russian Army on the 115th Vyazma Infantry Regiment.

[3] Sīmansons participated in the Russo-Japanese War, where he suffered a contusion during combat operations.

[4] Promoted to major general in May 1915, at the same time he was appointed commander of the 2nd Brigade of the 17th Infantry Division.

Sīmansons arrived in Riga on 8 January, and on 6 June he joined the Latvian National Armed Forces.

On the night of 9–10 October General Sīmansons revoked this order because he had decided to resist Bermondt's forces and defend Riga.

[9] After leaving the post of Commander-in-Chief, he continued his service on the Military Council of the Republic of Latvia.

On 13 January, at 2:10 pm, at the age of 73, General Sīmansons died at the Riga War Hospital.

[14] On 18 January he was buried in the Brothers' Cemetery in Riga in honor of his service of Latvia.