Leonard J. Prusak (1914 Minnesota), a resident of St Louis County, Minnesota, enlisted as a Private (S/N 17025142) in the U.S. Army Infantry on 11 February 1941 at Fort Snelling, Minnesota. He was single and had completed 2 years of college.

With war with Japan looming on the horizon, Private Prusak was sent to the Philippines almost immediately. In April 1941, the USAT Republic and the President Pierce docked at Pier 7 in Manila. Aboard were over 3000 men, about 700 of whom joined the 31st Infantry. Private Prusak was assigned to Company A, 31st Infantry Regiment and was stationed in Manila at Cuartel de España. All were soon sent to Fort McKinley's B Range for two months of basic training under the regiment's own COs, a task that consumed most of the cadre's time until late June.
In the summer of 1941, the tempo of training picked up.

"HAWAII BOMBED–WAR!" War with Japan broke out in the Philippines on 08 December 1941. The 31st Infantry remained in the Manila area as a security force while things deteriorated rapidly in other part of Luzon. By the middle of December the 31st Infantry Regiment was transferred to the Bataan Peninsula as part of War Plan Orange. The USAFFE defense plan for Bataan included the establishment of a Main Line of Resistance from Mauban on the western coast to the area north of the village of Abucay in the east. The Abucay Hacienda area was the site of one of the fiercest U.S. ground engagements in the early months of the war.

In the middle of January, the 31st Infantry Regiment was tasked to counterattack the Japanese 141st Infantry where they had breeched the Abucay Line in the area of the Capitangan River Valley along the Balantay River.

18 January 1942 – in the vicinity just north and east of Abucay Hacienda, Bataan.
"The 1st Battalion's other companies fared little better. Advancing into an open field in front of A Company, Lieutenant Charles Litkowski, Corporal Robert H. Dickson, and Private Leonard Prusak were cut down by a burst of machinegun fire. Litkowski and Prusak were both hit in the head and killed instantly..."
Source: The Birth of the 31st Infantry Regiment and Beyond, chapter 6, page 21.

After the war the remains of Private First Class Leonard J. Prusak were not recovered. He is memorialized on the Tablets of the Missing - United States Army and Army Air Forces at the Manila American Cemetery in the Philippines.

He also has a cenotaph in Calvary Cemetery, Chisholm, St. Louis County, Minnesota.