Gaius Julius Caesar defeated Gnaeus Pompeius Magnus and the Senatorial forces at the battle of Pharsalus in 48 B.C. and solidified his control over the Mediterranean world.
Pompey and the Senate's army had left Italy for Greece in 49 B.C. Caesar, for lack of a fleet, solidified his control over the western Mediterranean - Spain and North Africa, specifically, before assembling ships to follow Pompey.
An indecisive winter (49/48) of blockade and siege followed. Pompey eventually pushed Caesar into Thessaly and at Pharsalus attacked. Caesar, though with a smaller army, prevailed. Pompey fled from Pharsalus to Egypt, where he was assasinated on the order of Pharaoh Ptolemy XIV Dionysus.