Combat Initiative or Combating Initiative?

The Oxford Dictionary defines initiative as "the ability to assess and act on factors independently; the power or opportunity to act or take charge before others do; an act or strategy intended to resolve a difficulty or improve a situation" and valor as "great courage in the face of danger, especially in battle." The twin explosions triggered a complex attack, and soon, the Marines were defending themselves from machine gun fire, rocket-propelled grenades, and mortar explosions. Inside was a well-equipped mobile trauma bay with all the equipment normally found in a small city hospital's emergency room and a trauma nurse and corpsmen, who began their work of life saving.