 By the late 1670s France became an increasing threat in the Caribbean, and Morgan took control of the defence of Port Royal.He declared martial law in 1678 and 1680 – both during his periods as temporary governor of the island – because of the threat of invasion, re-built the fortifications surrounding the town, and increased the number of cannon from 60 to more than 100 in the five years up to 1680.In the 1670s and 1680s, in his capacity as an owner of a large slave plantation, Morgan led three campaigns against the Jamaican Maroons of Juan de Serras.