go to bat

verb3

1. •
   To be the individual or team that is currently batting; to play offense.

   • Robinson went to bat for the last time that day in the eighth inning, singling for his fourth straight hit. — 1968
2. •
   To champion, to actively assist, to provide support (for someone).

   • Among foremen who often “go to bat” for their men, encouraging efficiency brings an improvement in group production norms — 1968
3. •
   (figurative) To be aggressive, to be assertive, to actively pursue a goal or action.

   • Barb, you have to hang in there kid. […] Two more weeks, maybe three, and we go to bat, Barb. — 1995