Upon landing in Alexandria in September 1799, Gaspard Lefebvre quickly secured the port city and convened a war council to determine the army's next move. Despite General Massena’s prudent advice to wait for Madjriti reinforcements, Lefebvre chose to advance immediately toward Cairo, unaware that the French government had declared him a traitor and instructed their allies to withhold all support. The march south was grueling, characterized by oppressive heat and the constant threat of Bedouin raids, but the French army proved its mettle at the Battle of El-Delengat. There, Lefebvre’s forces withstood a massive charge by Egyptian cavalry before launching a devastating counter-attack that cleared the path to the capital.

The campaign for Cairo culminated in a decisive engagement outside Giza on October 16th. Lefebvre employed a deceptive strategy, concealing General Dubois’ cavalry division behind the terrain while his infantry formed defensive squares to absorb the Egyptian assault. As the Sultan’s forces committed to breaking the squares, the hidden French cavalry struck their rear, encircling and annihilating the Egyptian army. Following the victory, Lefebvre occupied Cairo, renaming it "New Gaul," but prioritized his personal agenda over administration. While his soldiers struggled with the local populace, he tasked his team of archaeologists with finding the specific ancient ceramic mug desired by his lover, a quest he successfully completed in December.

In early 1800, Lefebvre launched an ambitious offensive south down the Nile to destroy the Kingdom of Sion, a key British ally. This campaign ended in disaster at the Battle of Kosti, where Sionite knights launched a surprise dawn attack that inflicted heavy casualties and forced a chaotic French retreat. Chased back to Cairo by Sionite and British forces, Lefebvre realized his position in Egypt was untenable. Rejecting a retreat to Alexandria due to the risk of being trapped by the Royal Navy, he instead marched his army northeast into the Levant, aiming to reach the safety of the Eastern Roman Empire.

The trek through the Levant was a desperate fighting retreat, marked by the capture of Sidon and a sacrificial stand at Acre. Lefebvre left a garrison at the fortress city to delay the pursuing British and Sionite armies, sacrificing those men to allow the bulk of his forces to cross the border into Roman territory. Once in Constantinople, Lefebvre negotiated with Emperor Palamas, securing a military alliance by capitalizing on Rome’s historical rivalry with Egypt. With the Eastern Roman Empire formally entering the war against Britain and Egypt, the battered French army was granted safe passage, departing on Roman ships in January 1801 to return to France.