British anti-invasion preparations of 1803–05 were the military and civilian responses in the United Kingdom to Napoleon's planned invasion of the United Kingdom. They included mobilization of the population on a scale not previously attempted in Britain, with a combined military force of over 615,000 in December 1803. Much of the southern English coast was fortified, with numerous emplacements and forts built to repel the feared French landing. However, Napoleon never attempted his planned invasion and so the preparations were never put to the test.