Federal forces have positioned artillery batteries on a barrier island near Charleston Harbor, S.C., and begun firing on Confederate-held Fort Sumter 150 years ago this week in the Civil War.

The prolonged bombardment will continue for weeks, though the Confederates remain stoutly entrenched in the massive-walled fort where the Civil War began in 1861.

The move comes as Union forces hope to penetrate the Charleston Harbor defenses and seize the city as part of a tightening blockade on Southern rivers and seaports.

The Associated Press, in a dispatch titled “Latest from Charleston,” reported on the artillery barrages. It said “the bombardment of Sumter … proceeds sluggishly” as Union fighters fortified their positions near the harbor. In between bouts of firing, there is calm, “everything perfect quiet except the occasional boom of the guns.”

Another dispatch said witnesses reported seeing several artillery shells strike Fort Sumter, “which caused the brick and mortar to fly profusely.”