Marx has been maintaining this nonviolent resistance stance since the first article in Neue Rheinische Zeitung back in June, in part bc he believed the reactionaries would definitely lose

However, counterrevolution rallies and two days later Marx admits he was wrong: [Marx - Confessions of a Noble Soul]

And two days after that, Marx is explicitly advocating violent resistence: [Marx - A Decree of Eichmann’s]

Source is Marx Engels Collected Works vol8. Its very interesting to see Marx and Engels operating as agitators/organisers rather than theorists