YOU SAID:

They have gone to tell him of the arrival of strangers

INTO JAPANESE

彼らは彼に見知らぬ人が来たことを知らせに行った

BACK INTO ENGLISH

they went to tell him that a stranger had come

INTO JAPANESE

彼らは見知らぬ人が来たことを彼に伝えに行きました

BACK INTO ENGLISH

they went to tell him that a stranger had come