RichThesaurus
keep a tight rein on
vs
rule with a rod of iron
keep a tight rein on
verb
To exercise strict control over; keep in check.
rule with a rod of iron
verb
To rule with stern severity.
How often have the words
keep a tight rein on
and
rule with a rod of iron
occurred in a corpus of books?
(source:
Google Ngram Viewer
)