The victory of Napoleon Bonaparte’s Democratic French army over the Most Serene Republic of Venice forced the latter to enter into a surrender treaty. In 1797, the Treaty of Campo Formio was signed, and the control of the castle passed from the Venetians to the Democratic French. Napoleon decided to partition the Ionian Islands into three departments (Départements français de Grèce), and under this arrangement, Lefkada was assigned to the department of Ithaca.
The French opponents of the clergy undertake various actions in all the annexed regions to secularize the state, desecrating churches and prohibiting various religious ceremonies. In the castle of Lefkada, they convert the Orthodox church of Agia Mavra and the Latin church of Pantokrator into warehouses for animal feed.
In July 1798, Russia and the Ottoman Empire formed an alliance to curb the expansion of Democratic France in the Mediterranean region.
The strategic takeover of the Ionian Islands, under French control since 1797, played a pivotal role in achieving their objective. The Russo-Turkish fleet, having seized Kythira, Zakynthos, Kefalonia, and Ithaca, arrived in the maritime area off the castle of Agia Mavra on October 13, 1798.
On that very day, a formidable contingent of Ottoman troops, sent by Ali Tepelenli, the Pasha of Epirus, establishes a camp nearby. By blockading the castle from both land and sea, the Russo-Turkish military leadership demands the prompt surrender of the besieged. The French fortress commander’s refusal and his commitment to defend to the last, infuriate the leaders of the allied forces, prompting them to initiate the siege.
On November 3, after 12 days of intense bombardment, the French supplies began to dwindle, while 12,000 men rushed to reinforce the Russo-Turkish side. Consequently, compelled to surrender the fortress, the French faced unfavorable terms in their defeat.
The soldiers of the garrison were sent to Constantinople as prisoners of war, while the Commandant and officers returned to France under the condition that they would not launch any further attacks against the Emperor of Russia, the Sultan of the Ottoman Empire, and their other allies until the end of the war.
Between 1800 and 1807, the flag of the Septinsular Republic flew over the ramparts of the fortress of Agia Mavra—a quasi-federal state with Turkey holding sovereignty and Russia serving as the guarantor power. However, Napoleon Bonaparte’s victory over Russia compelled Tsar Alexander I to seek a truce. As a result, in July 1807, the Septinsular Republic fell under the control of the Imperial French. During their three-year occupation of the Agia Mavra fortress (1807-1810), they refined its fortifications by incorporating new military equipment.
In 1806, the allied bonds between the Russians and the Turks crumbled, and Ali Pasha, influenced by French diplomacy, turned against the Russians. He gradually gathered troops and undertook preparatory work. In the early months of 1807, and within a very short period, he constructed two new fortifications on hilltops.
The «Tekes» fortress or “Griva’s” castle and the castle of Agios Georgios Plagias. Both had direct visual contact with the fortress of Agia Mavra. Shortly before, he had erected the fortress of Aktio on the Acarnania side, and opposite, in Preveza in 1807, the castle of Pantokrator. With the swiftly organized defensive fortification network, Ali Pasha aimed to control the broader region of the Ambracian Gulf.
In response, the Russians, led by General Stutter, anticipating Ali Pasha’s impending attack, constructed in the same year what is known as the “new fortress” roughly in the middle of the southern arm of the Lefkada channel, and four coastal gun emplacements in Gyra.