Modrzejewski joined the Marine Corps Reserve in 1955 while at the University of Wisconsin-Milwaukee, and was a member of the Platoon Leaders Class; upon graduation in June 1957, he was commissioned a second lieutenant.

[2] In a White House ceremony on March 12, 1968, President Lyndon B. Johnson presented the Medal of Honor to two Marines for their actions in Vietnam — Major Modrzejeski and Second Lieutenant John J. McGinty, III.

That evening a numerically superior enemy force counterattacked in an effort to retake the vital supply area, thus setting the pattern of activity for the next two and one-half days.

Despite numerous casualties, a dwindling supply of ammunition and the knowledge that they were surrounded, he skillfully directed artillery fire to within a few meters of his position and courageously inspired the efforts of his company in repelling the aggressive enemy attack.

Although his unit was outnumbered and weakened by the previous fighting, Major Modrzejewski reorganized his men and calmly moved among them to encourage and direct their efforts to heroic limits as they fought to overcome the vicious enemy onslaught.

Again he called in air and artillery strikes at close range with devastating effect on the enemy, which together with the bold and determined fighting of the men of Company K, repulsed the fanatical attack of the larger North Vietnamese force.

His unparalleled personal heroism and indomitable leadership inspired his men to a significant victory over the enemy force and reflected great credit upon himself, the Marine Corps and the United States Naval Service./S/ LYNDON B. JOHNSON In 2004, the UWM Alumni Association honored Modrzejewski with a Distinguished Alumnus Award.