take the field

Enter a competition, as in The country's best spellers took the field in the national spelling bee. This term originated around 1600 when it meant "to open a military campaign." The field here is the field of battle. The term has been used figuratively almost as long, the first recorded use being in 1614.

The verb has 2 meanings:

Meaning #1: go on a campaign; go off to war
  Synonym: campaign

Meaning #2: go on the playing field, of a football team