@ChrisMckiernan Rather than a time ship, it seems to me like the modern soldiers interrupted the fight between the two tentacled entities. We can't be sure if any of the humanoids we see are/were actually human. From the visuals we are given, it would appear that the "samurai" is the intended target all along. We can only speculate why.
While I enjoyed the twist ending, I found the random flailing of the tentacles in the fight scene humorous, which really took away a lot of the suspenseful atmosphere. Near the end of the video, the way the rifles are held looks a bit odd. The guns look abnormally elongated and seem to be resting above the shoulder. I'm not a gun nut, so I could be misinterpreting things.