Pax Francorum

Background and OTL
In 1800, the French Revolution was in full swing, as were the French Revolutionary Wars. France was at odds with a wide array of opponents, chiefly the United Kingdom, whose Royal Navy prevented any kind of attack from the French. However, the French had won victories over many nations over the past few years, and stood a decent chance at dealing damage to the Brits should they find a way to cross the channel. Unfortunately for them, one fatal mistake on the part of their best general, Napoleon Bonaparte, cost them any opportunity to do so in the future.

Engineer Robert Fulton was in France at the time and planned on getting funding from the French government to advance his ideas. He showed them off to several people, and promised that his designs for submarines and naval ships in particular would prove deadly against enemy ships. However, the most important person he spoke to, Napoleon Bonaparte, was thoroughly unimpressed with Fulton. He had created a prototype submarine, which he named the Nautilus, and due to a small flaw in the hull, water leaked in and it had to be deconstructed. It was just days after this that Bonaparte arrived, saw no intact submarine, and wrote Fulton off as a fraud, ecausing him to go work for the British instead.

In this TL, however, the Nautilus does not leak and Napoleon arrives, sees it in action, and appeals to the French government to fund Fulton's ideas, which eventually allows the French Navy to become one of the greatest and most advanced in the world for its time.

Point of Divergence
In July 1800, Napoleon returns from fighting in Italy and arrives in Paris for a brief time to meet with Robert Fulton about his proposed work for the French Navy. Fulton tells him of multiple future plans, most notably the steam powered warship, and shows off his proudest achievement, the Nautilus, which was the first effective submarine, equipped with a primitive version of torpedoes.

Napoleon, being thoroughly impressed with what he saw and recognizing its great potential, immediately began funding the project and asked Fulton to mass produce these weapons for naval use against the British. The French Revolutionary Wars continued, and by 1803, Fulton and his workers had produced about 35 submarines able to be used in combat, and many more that were deemed unfit and unsafe, and a Submarine Division was officially added to the French Navy (all of this was largely unknown to the British, as to maintain the element of surprise that Napoleon loved so much).

The consequences of these advancements were not seen immediately, as the existing French government was much more concerned with issues in continental Europe. The French saw any possible engagement with the Royal Navy to be an impossible fantasy, and Napoleon was ridiculed when he made the suggestion, so the submarines essentialky just sat at port collecting dust, although they were maintained and improved regularly. However, when Napoleon became the Emperor of the French in 1804, this changed. He set his sights on the United Kingdom and planned to defeat them once and for all.

He now had a difficult choice to make: play it safe and allow the British to form coalitions and try to defeat them one by one until they had no choice but to accept him, or strike at his enemy's heart and attack the British, effectively ending any possibility of his defeat in the near future but at a high risk.