He was closely associated with a number of fellow officers who changed sides, abandoning their allegiance to James II.
Wharton's Regiment landed with a major expedition under Marshal Schomberg near Belfast and captured Carrickfergus.
In 1691, the regiment served during the Aughrim campaign and the decisive Siege of Limerick which ended the war with the Jacobite Irish Army surrendering.
In 1692, Brewer was identified as being part of a group of officers who were reportedly prepared to switch sides and assist a restoration of James II to the throne.
Ironically many of these officers were those such as John Lanier and Charles Churchill who had previously actively supported William during the Glorious Revolution.