Old sci fi short. Alien constantly evolves to combat an ex marine on Earth

Question

Read this in the 70's but (somehow) felt it was a bit older.

Protagonist driving late one night and this alien thing with tentacles attacks so he kills it with his pick-up.

Next day police and authorities are at his house looking for him but his wife hasn't seen him. He was witnessed dumping dead alien outside the small town police station. They ask if he mentioned this when he got home and she's all "that impossible man!" Because he hadn't even told her.

The story progresses with sightings of him around the vicinity every few hours, with dead aliens killed in a variety of ways. Experts realise the creature is sending fresh versions of itself with countermeasures to it's previous deaths but the protagonist is always ready with a new means of killing it.

Army intelligence have his records and know he is capable of something called King Marine Syndrome, such people, under the right stimuli, can win major battles.

They anticipate the next alien appearance and set things up. He is in a small boat (I think) crossing to a forest alien craft site. Just before he reaches it the high command shell the area in a long salvo, this does no good to his stealthy approach and induces in him the feeling that high brass always messes up and he is on his own. King Marine mindset emerges!

He gets to alien craft and it emerges for another round. This time he instantly drops his weapon and (kneels?) concedes.

This action changes alien intentions for future hostilities - IIRC

Thanks

Answer 1

The story is The Replicators by A. E. Van Vogt.

The opening paragraph in which the protagonist Matlin first kills the alien is:

Standing there, after killing the monster, Matlin began to get mad. In its death throes, the twelve-foot creature had done a violent muscular convulsion and somersaulted over into the dump section of Matlin’s truck. There it lay now, with its elephantine head and quarter-length trunk twisted to one side, and a huge arm and hand flung up and visible over the rear end. What must have been tons of shiny, black body was squashed limply down into the bottom of the cavernous metal carrier . . . creating a problem. That was all it was to Matlin: a problem.

The reference to the King Marine syndrome comes when the army start shelling the alien ship to deliberately induce King Marine Syndrome in Matlin (this is General Day speaking):

"A king Marine, Mr. Graham, can direct a war, take command of a city, or negotiate with a foreign power like a government. Marines who get to be generals are considered sub-level versions of this species. All Marines understand this perfectly. It will not occur to Matlin to consult me, or you, or the U.S. Government. He’ll size up the situation, make a decision, and I shall back him up.”

He turned to the major, commanded, “All right, start firing!”

At the end Matlin doesn't exactly surrender, but he throws his gun down as a gesture of friendship:

As he saw the creature, Matlin used his gun for the purpose that he had brought it. Deliberately, he tossed it down. It struck the metal floor with a clatter. The echoes of the sound faded — and there was silence. Alien and human stood there staring.

The full text is available here.