He loved books, but with the rumors of war he joined the National Guard at the age of 17.

After being discharged on November 19, 1864, Haven returned home to New London and worked for the Wilson Manufacturing Company, with which he was connected for 18 years.

On November 25, 1861, he enlisted in Company C, 1st Cavalry Regiment, Connecticut, and was made corporal on February 11, 1864.

On April 14, 1865, he became a member of Company D, Third Regiment of National Guards, and was made First Sergeant eight days later.

After resigning on April 21, 1873, he rejoined the Guards and was made captain and adjutant on February 18, 1879; Major, March 20, 1882; Colonel, July 12, 1886; Brigadier-General, commanding the brigade, on May 28, 1892.