She possessed, like Margaret, a strong character, statesmanlike qualities and singular capacity in the administration of affairs.

She filled the difficult post of regent for the whole period of twenty-four years between the death of Margaret and the abdication of Charles V in 1555.
It was fortunate indeed for that great sovereign that these two eminent women of his house should, each in turn for one half of his long reign, have so admirably conducted the government of this important portion of his dominions, as to leave him free for the carrying out of his far-reaching political projects and constant military campaigns in other lands.

Two years after Mary entered upon her regency Charles appointed three advisory and administrative bodies--the Council of State, the Council of Finance and the Privy Council--to assist her in the government.

The Council of State dealt with questions of external and internal policy and with the appointment of officials; the Council of Finance with the care of the revenue and private domains of the sovereign; to the Privy Council were entrusted the publication of edicts and "placards," and the care of justice and police.
When Charles succeeded Philip the Fair only a portion of the Netherlands was subject to his sway.

With steady persistence he set himself to the task of bringing all the seventeen provinces under one sovereign.