In England Charles I was having great difficulty
maintaining control over his parliament. Both the Scottish
and English parliaments were aggressively Protestant, and
victory for them over the king would have dire consequences
for the Ulster Irish. Seeing England's difficulty as Ireland's
opportunity the Ulster Irish, under Sir Phelim O'Neill,
rebelled and initially met with considerable success.
After securing Ulster, Sir Phelim O'Neill
marched on Drogheda where he was joined by the Old English
and Anglo-Irish, who also feared the growing power of the
English parliament.