The War of 1812 might not have happened without the Slave Trade Act of 1807.
In 1807, the British Parliament passed a law against the slave trade, although not against slavery itself.
This law came after many years of a campaign for the abolition of slavery that had been fought in England, led by William Wilberforce. The abolitionists really wanted the end of slavery, but their motions were defeated year after year.
In 1807, Britain was at war with France, and no British ships were allowed to trade with the French. Many British slave ships had converted to the US flag in order to continue selling slaves to French colonies. The slave trade was particularly important to the French Colonies, because the slave ships that sold the slaves also transported the sugar that the colonies produced.
The abolitionists backed an anti-slave trade law that was promoted as a way to cripple France's trade. The Slave Trade Law of 1807 said (among other things) that it was illegal for any British subject to be involved with the slave trade.
While researching this aspect of history, I was confused about the actual enforcement. On the internet, I found references to slave captains being fined a fixed amount for each slave aboard their ship, which apparently led to slave ship captains throwing slaves overboard to avoid fines. On the other hand, the Slave Trade Act of 1807 clearly states that any slave ship shall be forfeit.
Also confusing was the fact that the Americans passed their own law against the slave trade the same year. But they were not in a position to vigorously enforce their law, like the Royal Navy was. Also, the war between Britain and France encouraged the enforcement of the anti slave trade law by Britain.
In any case, it resulted in increased searches and seizures of ships flying the American flag, by the British navy.
There is also a connection with Sierra Leone, as the city of Freetown was the place that slaves on seized ships were set free by the Royal Navy.
Royal Navy ships continued to stop and search American ships for several more years, and became one of the well-known causes of the US government declaring war on Britain in 1812. What is not so well known is that there was a connection between the war of 1812, and the campaign to abolish the slave trade.
The abolitionists' campaign carried on, and eventually, the actual practice of slavery would be declared illegal.