There seems to be an inclination to insist the OP’s perfectly valid question is not what it is, so maybe we can define our terms.
The order of battle of a large military formation will generally divide the subordinate units into combat arms, comabt support, and service support (the terms may differ from country to country but that’s the jist.) Combat arms are what the OP is likely referring to - people whose speciality is actually engaging the enemy and taking and holding ground. Infantry, armor, reconnaissance units.
Service support are the folks the OP is definitely NOT talking about - logistics, supply, transport, medical, field kitchens, administration, and the like. Yes, most carry weapons and are trained in basic combat, but that is obviously not what the OP is asking.
Combat support, as the name would suggest, is where we have a grey area. Artillery, for instance, is grouped into combat support in some org charts, despite being rather obviously (to me) a combat arms role. Engineers are invariably classed as combat support though they’re often front line troops. Electronic warfare is combat support but is clearly not front line the way engineers are. So one could argue over units in that group.