2 adjectives to describe insistency

He explained that the United States Government was resolved not to have a direct or indirect war with the Creeks; and he closed by reiterating, with futile insistency, that the instruction to the Cherokees not to permit Creek war parties against the whites to come through their country, did not warrant their using force to stop them.

The words drilled themselves into his brain with relentless insistency.

2 adjectives to describe  insistency