take over/up the reins idiom       
 控制;接管(某东西,尤指某机构或国家)
to take control of something, especially an organization or a country
  He took up the reins of government immediately after the coup. 在那次政变之后,他立即控制了政府。 
 Synonyms: check (LIMIT)constraintcontrol (POWER)curb (CONTROL)curtailmentlimit limitationrestraintrestriction