Enlisting as a private in the 99th Ohio Volunteer Infantry in 1862, Van Fossen was seriously wounded at the Battle of Nashville. He was discharged as an orderly sergeant after three years of service. "Mr. Van Fossen, through disability caused by service in the army, has been unable to perform much labor, but having a competence for himself and wife…they are living a retired life, in the enjoyment of the labor of the past" (Sutton's History). He was a charter member of the Neal Post of the Grand Army of the Republic.

Highly regarded by his fellow citizens followed Van Fossen through his retirement. He was a featured participant in the cornerstone ceremony for the Monumental Building. "Sergt. W. M. Van Fossen, who in the procession was color-bearer of the Ninety-ninth regiment, veiled the corner-stone with the flag, saying, 'Done in memory of the fallen heroes of Shelby county, in the State of Ohio and town of Sidney, June 24th in the year of our Lord 1875'" (Hitchcock's History of Shelby County). The old soldier passed away on February 6, 1906, and was buried at Graceland Cemetery.

Unlike Van Fossen, General Walker, the filibustering leader, did not live to "enjoy the labor of the past." After several unsuccessful attempts to invade Nicaragua, Walker surrendered to a British naval officer who turned him over to Honduran authorities. A firing squad performed its duty before an adobe wall on September 12, 1860, and Walker with all his ambitions was buried in an unmarked grave.