He was immediately wrapped up in the politics of the day, a time when the politics were literally cut-throat.
He was often irresolute, suspicious of everyone, and dependent for advice on his brother's widow, Donna Olimpia Maidalchini.
Because some of the corrupt officials were known to slip outside the papal states with public money, he issued a bull ordering that cardinals who left without permission could not return for six months, and were put on a course to lose their cardinalate and all its perks.
The French objected so strongly that troops were sent to the Papal States.
On 26 November1648 he issued a bull which nullified the articles in the Peace of Westphalia that were against Catholicism.
On 31 May1653 he condemned five propositions from the "Augustinus" of Jansenius, which helped start the great Jansenist controversy in France.