They included Brill (Brielle) in Holland and Flushing (Vlissingen) and Fort Rammekens on the nearby island of Walcheren.
English and Scottish volunteers serving with the Dutch Protestants against Spain helped capture Brill, Rammekens and Flushing in 1572 and garrisoned them soon after.
[2] In the Treaty of Nonsuch, the Dutch effectively ceded control of the three towns to Elizabeth I as security for her assistance and it was agreed that England would garrison them at its own expense.
[2] When the 1604 Treaty of London ended the Anglo-Spanish War, the Spanish demanded the Cautionary Towns be returned to them but the English refused.
[4] Philip III of Spain eventually conceded the point, having decided their neutrality permitted him to gain access to the English Channel.