{pa' 'elDI' 'avwI', jISuvrupchoH} {pa' 'el 'avwI', ghIq jISuvrupchoH} {pa' 'el 'avwI', ngugh jISuvrupchoH}
the only difference between the {vaj}/{mo'} method, and the last three is perhaps that the {vaj}/{mo'} are more direct, while the rest only imply/indirectly mean that the guard's entrance to the room was the reason of my "becoming ready to fight".
Along with Sustel's reply, I will add that -DI', ghIq, and ngugh describe WHEN you get ready to fight, not WHY. The timing could be coincidence, and not cause/effect. Also with vaj/-mo' (at least to me), while some uses could be done with either one, I still see a difference. "I saw the signal (that warns that the enemy is coming), so I got ready to fight." You could use either vaj or -mo'. I would use vaj. I don't get ready to fight /because I saw the signal/. I get ready to fight /because the enemy is on the way and battle is about to begin./ But this part could be just me. - DloraH