invade, inveighed

Invade or invade means to enter as an enemy, forcibly and with hostile intent--
His plans to invade Ruritania were deemed ludicrous; no one took them seriously.
He worries a lot about what will happen if terrorists invade out country.

Inveighed or inveighed ( rhymes with invade ) is the past tense ( yesterday, or some time ago ) of "inveigh", meaning to protest strongly, in words, or to argue passionately--
Every April he inveighed against taxation to anyone who would listen.
He made a speech, in which he inveighed against all forms of political corruption.

Now that you know that, you can say--
"In the 1930's, he inveighed against isolationism, and warned that an enemy might invade the United States."