The eastern end of the former channel became the town and harbour (from 1820) of St Sampson's, now the second biggest port in Guernsey. The roadway called "The Bridge" across the end of the harbour at St Sampson's recalls the bridge that formerly linked the two parts of Guernsey at high tide.
New roads were built and main roads metalled for ease of use by the military.
In December 1651, with full honours of war, Castle Cornet surrendered - the last Royalist outpost anywhere in the British Isles to surrender.
Wars against France and Spain during the 17th and 18th centuries gave Guernsey shipowners and sea captains the opportunity to exploit the island's proximity to mainland Europe by applying for letters of marque and turning their merchantmen into privateers.
The occupying German forces deported over 1,000 Guernsey residents to camps in southern Germany, notably to the Lager Lindele (Lindele Camp) near Biberach an der Riß and to Laufen.During the Middle Ages, the island was a haven for pirates that would use the "lamping technique" to ground ships close to her waters.This intensified during the Hundred Years War, when, starting in 1339, the island was occupied by the Capetians on several occasions.In the mid-16th century, the island was influenced by Calvinist reformers from Normandy.
During the Marian persecutions, three women, the Guernsey Martyrs, were burned at the stake for their Protestant beliefs.During the English Civil War, Guernsey sided with the Parliamentarians.