Shortly after dawn Melas began to pour his troops across the Bormida, and drove in the French outposts on Marengo:  but there they met with a tough resistance from the soldiers of Victor’s division, while Kellermann, the son of the hero of Valmy, performed his first great exploit by hurling back some venturesome Austrian horsemen into the deep bed of the Fontanone.  This gave time to Lannes to bring up his division, 5,000 strong, into line between Marengo and Castel Ceriolo.  But when the full force of the Austrian attack was developed about 10 a.m., the Imperialists not only gained Marengo, but threw a heavy column, led by General Ott, against Lannes, who was constrained to retire, contesting every inch of the ground.  Thus, when, an hour later, Bonaparte rode up from the distant rear, hurrying along his Consular Guard, his eye fell upon his battalions overpowered in front and outflanked on both wings.  At once he launched his Consular Guard, 1,000 strong, against Ott’s triumphant ranks.  Drawn up in square near Castel Ceriolo, it checked them for a brief space, until, plied by cannon and charged by the enemy’s horse, these chosen troops also began to give ground.  But at this crisis Monnier’s division of 3,600 men arrived, threw itself into the fight, held up the flood of white-coats around the hamlet of Li Poggi, while Carra St. Cyr fastened his grip on Castel Ceriolo.  Under cover of this welcome screen, Victor and Lannes restored some order to their divisions and checked for a time the onsets of the enemy.  Slowly but surely, however, the impact of the Austrian main column, advancing along the highroad, made them draw back on San Giuliano.

By 2 p.m. the battle seemed to be lost for the French; except on the north of their line they were in full retreat, and all but five of their cannon were silenced.  Melas, oppressed by his weight of years, by the terrific heat, and by two slight wounds, retired to Alessandria, leaving his chief of the staff, Zach, to direct the pursuit.  But, unfortunately, Melas had sent back 2,200 horsemen to watch the district between Alessandria and Acqui, to which latter place Suchet’s force was advancing.  To guard against this remoter danger, he weakened his attacking force at the critical time and place; and now, when the Austrians approached the hill of San Giuliano with bands playing and colours flying, their horse was not strong enough to complete the French defeat.  Still, such was the strength of their onset that all resistance seemed unavailing, until about 5 p.m. the approach of Desaix breathed new life and hope into the defence.  At once he rode up to the First Consul; and if vague rumours may be credited, he was met by the eager question:  “Well, what do you think of it?” To which he replied:  “The battle is lost, but there is time to gain another.”  Marmont, who heard the conversation, denies that these words were uttered; and they presume a boldness of which even Desaix would scarcely have been guilty to his chief.