The siege of Utica (49 BC) was a short-lived attempt by Caesar's lieutenant in North Africa, G. Scribonius Curio, to take advantage of his victory in a battle outside the city (Great Roman Civil War).
After clearing Pompey's men out of Sicily Curio crossed over to North Africa with two of his four legions, and advanced from Cape Bon towards Utica. In a curious decision Curio chose to take two legions that had only recently changed sides, having only join Caesar's cause during his advance down Italy.
Pompey's army in North Africa was commanded by P. Attius Varus, who also had two legions at his disposal around Utica. He could also rely on support from King Juba of Numidia, who had agreed to support Pompey, and who had a personal grudge against Curio (when serving as Tribune Curio had attempted to pass a law that would have turned Numidia into a Roman province).
When Curio arrived outside Utica Varus thought he had a chance to persuade his two legions to change sides for a second time. The two armies drew up in lines of battle outside the city on two occasions - the first saw Varus attempt to convince his opponents to change sides, while the second erupted into an open battle (battle of Utica). This ended in victory for Curio, and Varus was forced to retreat back into the city, even abandoning his fortified camp outside one of the gates.
On the day after this battle Curio began to construct siege lines outside the city. This caused a great debate inside the city, where support for Pompey was by no means universal. The citizens only decided to resist when news reached them that King Juba was on his way with a relief army.
The same news reached Curio, but for some time he refused to belief it and pressed on with the siege. Juba was able to reach within twenty miles of the city without being detected. When Curio finally realised that Juba was indeed close by he sensibly decided to abandon the siege and retreat to a strong position at the Cornelian Camp, used during the Roman siege of Utica 150 years earlier. This move should have secured his position, but Curio was mislead by false information that Juba had been forced to turn back with most of his army. Leaving his secure camp Curio advanced towards what he believed was a small Numidian force, only to run into Juba's main army. The resulting battle of the Bagradas River was a major defeat for Caesar's men. Curio was killed and Caesar's entire position in North Africa was destroyed.