Homecoming Horde

Haverford knew from his radio contracts he was the last man alive on Earth. His death was certain—for the enemy numbered trillions, a—
The room was sealed as tightly as possible. Haverford had checked it for cracks, made sure the windows were caulked, and now kept constant guard. He was alone. He could never tell when the alien invaders would break through.
I must be nearly the last , he thought. It was strange, this feeling of being alone on Earth. But it was probably true.
The aliens had come six days before. Haverford remembered picking up their ultimatum on his ham set:—
EARTHMEN, THE LANTHAII ARE COMING. BEWARE!
That was all it had been—an ominous warning, rather than a threat or an order. The way the message had been worded left little doubt that they were conquerors—conquerors from space.
Haverford had been amused, at first. A solitary recluse, he had little dealings with his fellow men, at least not in person. The costly ham set that occupied nearly a third of his one-room flat was his sole contact. Through radio he kept in regular touch with friends in Yokohama and Buenos Aires, Texas and Oregon, while actually leaving the confines of his own room at increasingly rare intervals.
He had, naturally, picked up the Lanthaii messages on his set. There wasn't an amateur operator in the world that hadn't detected them. That was when he began to feel it wasn't a joke.
Reports came in. Dazo Osaki, the Japanese contact, reported hearing the strange message; Lionel Bentham in Sussex picked it up also, as did Miguel Bartirone in Buenos Aires. EARTHMEN, THE LANTHAII ARE COMING. BEWARE! Someone—there was no doubt of it—was beaming the message at the entire Earth from outside .
And then the Lanthaii had come.
Haverford, pacing his room nervously, remembered the day of their landing. He had been talking to Bentham, the Englishman, a slow-speaking, phlegmatic sort.
—so I mean to write to my man in Parliament, y'know, and ask him to plump for the legislation. It'll be a great boon for ham operators if—Lord! What's that! What's that?