He led a squad when his unit moved forward in darkness to meet the threat of a breakthrough by elements of the 17th German Panzer Grenadier Division. Assigned to protect the left flank, he discovered hostile troops digging in. As he reported this information, several German machineguns opened fire, stopping the American advance. Knowing the position of the enemy, Sgt MacGillivary volunteered to knock out 1 of the guns while another company closed in from the right to assault the remaining strong points. He circled from the left through woods and snow, carefully worked his way to the emplacement and shot the 2 camouflaged gunners at a range of 3 feet as other enemy forces withdrew. Early in the afternoon of the same day, Sgt MacGillivary was dispatched on reconnaissance and found that Company I was being opposed by about 6 machineguns reinforcing a company of fanatically fighting Germans. His unit began an attack but was pinned down by furious automatic and small-arms fire. With a clear idea of where the enemy guns were placed, he voluntarily embarked on a lone combat patrol. Skillfully taking advantage of all available cover, he stalked the enemy, reached a hostile machinegun and blasted its crew with a grenade. He picked up a submachinegun from the battlefield and pressed on to within 10 yards of another machinegun, where the enemy crew discovered him and feverishly tried to swing their weapon into line to cut him down. He charged ahead, jumped into the midst of the Germans and killed them with several bursts. Without hesitation, he moved on to still another machinegun, creeping, crawling, and rushing from tree to tree, until close enough to toss a grenade into the emplacement and close with its defenders. He dispatched this crew also but was himself seriously wounded. Through his indomitable fighting spirit, great initiative, and utter disregard for personal safety in the face of powerful enemy resistance, Sgt. MacGillivary destroyed four hostile machineguns and immeasurably helped his company to continue on its mission with minimum casualties.

MacGillivary died on June 24, 2000 in Brockton, MA and is buried at Arlington National Cemetery. His membership was sponsored by his nephew, Ron MacGillivary.