Although 'combat' here is a metaphor for an intense competition, many forms of hand-to-hand combat end up with the opponents physically interlocking their weapons and/or arms and legs.
'Locked' is also a possible reference to various species of deer who physically interlock their antlers when asserting dominance. People have actually encountered bucks with their racks so intertwined that it required human intervention to physically separate them. Otherwise, they both just end up eventually dying if they cannot separate themselves. Sometimes one of them ends up killing the other one, then can't disentangle himself from the dead one.
Here's a (non-fatal)
video of deer literally locked in combat. It's rather unusual in that it's taking place in an suburban environment, but you can see at a couple points where they're so entangled they can't disengage, although they eventually break free and the loser runs off.
Warning: Although it's not especially graphic (no blood, injuries, or fatalities) it does contain animals fighting, so don't watch if bothered by such.