He was inspector of ordnance and equipment for the reconstruction of three Spanish Navy gunboats raised by Admiral George Dewey after the Battle of Manila Bay during the Spanish–American War.

He was the first commanding officer of the scout cruiser USS Birmingham from April 11, 1908, to May 9, 1909, and Captain of the Yard at Naval Station New York from May 9, 1909, to October 28, 1909.

When President Woodrow Wilson requested that a Joint session of the United States Congress declare war on the German Empire and Congress approved the declaration on April 2, 1917, bringing the United States into World War I, Walling returned to duty as Inspector of Engineering and Ordnance Material at Boston, Massachusetts until November 18, 1919.

Naval Academy, Midshipman Walling was assigned in December 1876 to the newly commissioned screw sloop-of-war USS Vandalia, stationed in European Squadron in the Mediterranean Sea.

[5] In June 1887, he joined the steam sloop-of-war USS Brooklyn, flagship of the Asiatic Squadron, aboard which he served until August 1888, when he was transferred back to Essex, which returned to New York City in April 1889.

[5] On February 2, 1894, Walling was aboard Kearsarge along with 202 other officers and men, including the admiral commanding the North Atlantic Squadron, when the ship was wrecked on Roncador Cay in the western Caribbean Sea off Venezuela.

[5] In April 1895, he was assigned to the protected cruiser USS Atlanta in the North Atlantic Squadron, and served aboard her until she was decommissioned in September 1895.

[5] In June 1899, he took a detachment of officers and men on board the hospital ship USS Solace for duty in the Philippine Islands, which the United States had seized from Spain during the war.

[5] After returning to the United States from the Philippines in June 1901, Walling served as executive officer on the protected cruiser USS Albany in the European Squadron in the Mediterranean Sea.

[9] At the outset of U.S. involvement in World War I on April 2, 1917, Walling returned to duty as Inspector of Engineering and Ordnance Material at Boston, Massachusetts until November 18, 1919.

[11] Walling was married on October 27, 1892, to Wilhelmina Boyd, daughter of a U. S. Navy captain, at Grace Church in Brooklyn, New York.

The Wallings had two daughters, Grace, who married U.S. Navy Commander James Sutherland Spore, and a younger sister, Bernice.