Bielaski was a friend of Abraham Lincoln, who gave him a commission in the Union Army when the American Civil War broke out in 1861.

Serving as an aide to Brigadier General John A. McClernand, Bielaski was killed while leading the 27th Illinois Infantry Regiment in a charge at the Battle of Belmont.

[7] After serving as a surveyor and engineer for the Baltimore and Ohio Railroad, he traveled to Florida for surveying work in 1835 before moving to Springfield, Illinois, in 1837.

Bielaski spent eighteen months in Mexico, where he was employed as an engineer and declined an offer of Mexican citizenship made by Santa Anna.

[4] When the American Civil War began in 1861, Lincoln offered Bielaski a captain's commission to serve in the Union Army.

Union Brigadier General Ulysses S. Grant wanted to contain the Confederate positions, and boarded men onto transport vessels on November 6, 1861.

A position near Belmont was reached on November 7, and the Union troops began moving to attack the Confederates, who were commanded by Brigiader General Gideon Pillow.

Buford decided to make the movement against the Confederate rear; the historian Nathaniel Cheairs Hughes believes that Bielaski supported the decision.

Hughes states that he was killed by a bullet to the head,[13] while Joseph A. Wytrwał, writing for Polish American Studies, attributes his death to a cannonball.

[9] Union Colonel John A. Logan stated "a braver man never fell on the field of battle" when writing about Bielaski's death in his action report, and McClernand also noted his bravery.

[14] Grant's men were initially able to capture the Confederate camp, but Pillow received reinforcements from Columbus and counterattacked, driving the Union soldiers from the field.