That is a term that refers to the ribbons worn by soldiers on their uniform above the LEFT pockect. These ribbons represent various Medals earned by the soldier. Some Medals are earned for bravery in combat, some are for serving in campaigns or Wars and some are issued in recognition. So, the term "combat" may refer just to the medals earned in war but not necessarily.
Another slang word for the variety of colorful ribbons is "salad".