The official history of the Royal Navy reached an important juncture in 1707, when the Act of Union merged the kingdoms of England and Scotland into the Kingdom of Great Britain, following a century of personal union between the two countries. This had the effect of merging the Royal Scots Navy into the Royal Navy. The Navy grew considerably during the global struggle with France that had started in 1690 and culminated in the Napoleonic Wars, a time when the practice of fighting under sail was developed to its highest point. The ensuing century of general peace saw Britain virtually uncontested on the seas, and considerable technological development. Sail yielded to steam and cannon supplanted by large shell-firing guns, and ending with the race to construct bigger and better battleships.