The invasion was planned by the Duc de Choiseul who became French foreign minister in December 1758 and effectively served as Prime Minister during the period of the mooted invasion.
He wanted to launch a bold initiative that would knock Britain out of the war with one stroke.
French pride had been stung the previous year by the ease with which the British had captured Louisbourg and launched amphibious raids on the French coast during 1758, such as that against Cherbourg.
British financial subsidies and military aid to her only ally Prussia had kept that country afloat since 1756.
Choiseul's brief as foreign minister was to overturn this situation.

Choiseul was interested in the concept of a French invasion of Britain.
He perceived that Britain's strength was its naval power.
He saw that if a large French force managed to cross the Channel without being intercepted, it could triumph over the relatively weak British land forces.
Choiseul initially ignored perceived wisdom that any invasion would have to involve French warships.
He believed that trying to bring warships out of the blockaded port at Brest would cause unnecessary delays, and could be disastrous.
A mixed force as he saw it would suffer the same fate as the Spanish Armada.
A previous attempt by France in 1744 had to be abandoned.

His conception was relatively simple: a massive fleet of flat-bottomed transport craft would carry an army of 100,000 troops across the Channel where they would be landed on the coast of southern England.
An essential component of the plan was speed.
The French would wait for a favourable wind and cross the Channel quickly.
Once they landed, they believed they would easily overpower the small army Britain retained on home soil and end the war.
Choiseul managed to overcome opposition in the French cabinet and the invasion was approved as the cornerstone of French strategy for 1759 along with an attempt to capture Hanover.
The invasion was planned by the Duc de Choiseul who became French foreign minister in December 1758 and effectively served as Prime Minister during the period of the mooted invasion. He wanted to launch a bold initiative that would knock Britain out of the war with one stroke. French pride had been stung the previous year by the ease with which the British had captured Louisbourg and launched amphibious raids on the French coast during 1758, such as that against Cherbourg. British financial subsidies and military aid to her only ally Prussia had kept that country afloat since 1756. Choiseul's brief as foreign minister was to overturn this situation.
Choiseul was interested in the concept of a French invasion of Britain. He perceived that Britain's strength was its naval power. He saw that if a large French force managed to cross the Channel without being intercepted, it could triumph over the relatively weak British land forces. Choiseul initially ignored perceived wisdom that any invasion would have to involve French warships. He believed that trying to bring warships out of the blockaded port at Brest would cause unnecessary delays, and could be disastrous. A mixed force as he saw it would suffer the same fate as the Spanish Armada. A previous attempt by France in 1744 had to be abandoned.
His conception was relatively simple: a massive fleet of flat-bottomed transport craft would carry an army of 100,000 troops across the Channel where they would be landed on the coast of southern England. An essential component of the plan was speed. The French would wait for a favourable wind and cross the Channel quickly. Once they landed, they believed they would easily overpower the small army Britain retained on home soil and end the war. Choiseul managed to overcome opposition in the French cabinet and the invasion was approved as the cornerstone of French strategy for 1759 along with an attempt to capture Hanover.
Planned French invasion of Britain (1759)