How did the Romans defend themselves from a siege?

Answer 1

A city would have walls surrounding it the majority of the time. There would be guards patrolling it, on the lookout.

There may have been a cohort based in the city and they would go to battle.

Answer 2

The siege tactics of the ancient Roman legions changed over the long span of time that ancient Rome was a power in the Mediterranean world. These changes were due to new weapons the Romans developed and the different tactics were often dependent on the military target to be taken or destroyed. A brief example of the latter will be followed by specifics. A gated city that needed to be conquered was usually given the chance to surrender. Conditions of surrender could differ depending on perhaps a wider view of the war Rome was engaged in. In many cases the Roman soldiers preferred that a city not surrender and be subject to a brutal invasion because in such a case the soldiers were entitled to all the booty they could find in the doomed city. Nevertheless the ancient Roman legions were specialized in siege warfare, more so than other large fighting forces in the ancient world.

In the earlier days of the Roman Republic, the best way to capture a fortified city was by a surprise assault or with the help of traitors within the enemy city. Another alternative if time permitted was simply to starve the enemy into submission.

The ideal scenario however was a Roman force aided by engineers specializing in siege warfare. As an aside, when Caesar was battling the Gauls, both Caesar and the opposing forces led by Vercingetorix applied starvation tactics on the fortified enemy armies. Caesar ended up being the last one standing as his starvation siege of the enemy succeeded.

Siege warfare was one turning point in the Roman siege of Jerusalem that began in 70 AD/CE. The Jewish rebels had early successes against the Romans. It took some time but eventually it became clear to Rome that earlier attempts to keep the city under Roman control were ineffective. Thus Titus was given the task of routing the rebels who controlled the fortified city of Jerusalem. High and thick walls protected the city. In this particular case Titus used assault ramps to build a "roadway" to the top of the walls and tried to over run the defenders. Jerusalem was a large and complex city and Titus had some successes and some setbacks with the ramps. He also used catapaults to launch heavy rocks against the defenders along with battering rams. It was a long siege but Titus eventually overcame the Jerusalem defenders and destoyed the city and the Temple.

The siege of the palace fortress of Masada was difficult due to the geography the fortress rested on. It was a fortified place with only a narrow road leading to the entrance. In this particular case the Romans had to build a huge ramp in order to finally breach the walls. It was a hollow victory as the rebels committed suicide rather than be captured.

The final siege weapon I shall mention was the moveable siege towers. Roman engineers constructed towers as tall as the protective walls of an enemy city. The tower was moveable and placed close to the walls of a fort or city and Roman soldiers would attack defenders who had used the height of their walls as an advantage over the Romans below the walls. The seige tower countered this advantage by elevanting the Roman attackers to the same height of the walls of defense.