In 1558, still in exile, Knox published The First Blast of the Trumpet against the Monstrous Regiment of Women, an attack on the legitimacy of female rule aimed specifically at the Catholic queens then governing England, Scotland and France, principally Mary I of England and Mary of Guise, regent of Scotland. The tract argued from scripture and natural order that government by women violated both, and it was blunt even by the standards of sixteenth century polemic.
The timing proved disastrous for Knox personally. Mary I died and was succeeded by Elizabeth I within months of the tract's publication, and Elizabeth, a Protestant queen who might otherwise have been a natural ally, never forgave its argument, which applied to her as much as to the Catholic queens Knox had actually been attacking. The First Blast damaged Knox's standing with English Protestantism for the rest of his career and complicated Scotland's relationship with England at a moment when Scottish reformers badly needed English support.
His later confrontations with Mary, Queen of Scots, after her return to Scotland in 1561, are often read through the same lens the tract created: a reformer whose theological bluntness about female rule shaped his reputation as much as any sermon he preached or confession he helped draft.