Rome Sends Aid to Saguntum

At the start of the Second Punic War, Hannibal besieged Saguntum.

I'll summarize the shape of the wall. There was a large wall roughly elliptical in shape. This main wall pointed outward. The city was divided into three sections by other walls, which allowed people on the walls to defend on either side. In one section, a citadel had the most impressive defenses. Additions to the main wall were made as extensions, These "outer wall" additions were not too high and the defenders might have stood only 2 meters above attackers. Due to extensive additions, the main wall is only exposed to the outside on one small section of its perimeter to one side.

A lot of what is known is from Carthaginian prisoners or Saguntum slaves freed by Romans after the war. They might not be true, but it's what the Roman writers knew anyways.

Hannibal took 8 months to take the city. That much historians are pretty sure about.

His forces consisted of African soldiers and Iberian mercenaries. Three attempts to storm the city failed, even against the weaker outer extension walls. After three months of siege, the Carthaginians captured the outer walls and 3/4 of the Saguntum food supply and most of their preserved meat, forcing the garrison to subsist on grain (and maybe rats). Later the main wall fell. Finally, after eight months, the citadel fell.

Rome heard about the news almost immediately but did nothing. Cynical historians say that Saguntum was sacrificed to allow Rome to have a Casus Belli against Carthage. Some point out Rome was busy fighting Illyria and an army was needed in Cisalpine Gaul to deter the Gauls from... whatever the Romans feared.

Let's suppose that Rome did send aid. They dispatch 2 legions from Illyria and 1 newly raised one to accompany some mercenary cavalry and arrive at Saguntum once the outer wall fell, but find themselves outnumbered 3 to 1, with no way to coordinate with the defenders. Hannibal gets seven days of notice between the Roman beachhead and the time the army gets to Saguntum.

What now?
 
Hannibal would probably do something akin to what Sertorius did at the siege of Lauro. He detaches part of the army so that the relieving force can’t help the besieged lest they’re attacked from behind. Then if the Romans were ever to split, may it be for foraging or whatever, Hannibal would send his men to cut off the supply line. The Roman main force would then be sent to aid the foragers, and Hannibal would have already laid an ambush for it, thus the Roman army gets virtually annihilated and Sagunto promptly surrenders.
 
Hannibal would probably do something akin to what Sertorius did at the siege of Lauro. He detaches part of the army so that the relieving force can’t help the besieged lest they’re attacked from behind. Then if the Romans were ever to split, may it be for foraging or whatever, Hannibal would send his men to cut off the supply line. The Roman main force would then be sent to aid the foragers, and Hannibal would have already laid an ambush for it, thus the Roman army gets virtually annihilated and Sagunto promptly surrenders.

Thanks for the reply!

Hmmm, with the terrain around Saguntum, it would seem unlikely that 1 or even 2 weeks notice is sufficient for Hannibal's scouts to properly asses the size of the Roman Army. Detaching part of an army to deal with a relief force while the rest is still pinned on the garrison is risky and against an army that could be bigger was often seen as reckless. If it goes wrong, he would have to have a plan for rearguard action (easy since he has the Numidian elite cavalry plus plenty of Iberian mercenaries)

However, Hannibal did beat some pro-Roman Gauls in OTL who blocked a place where he could ford alongside a thin bridge (think triple file on the bridge with all the armor) by... detaching a force that three days prior went to find another fording point. In that case he knew he was outnumbered and pulled it off successfully. Once he saw the signal, the main army forded and the river basically pinned them since fording back in melee would be hard and the detatchment slammed into the Gauls, scattering them. Hannibal also wasn't afraid to split up his army in Trebia and Lake Trasimene.

So I can see him easily making that decision, not knowing the size of the enemy. And fortunately for him in this case, he didn't lose 70% of his army crossing the Alps yet and outnumbers the Romans 3 to 1 (albeit, a good half would be pinned to the garrision) I don't know if the Romans would send out vulnerable foragers. If they did, I can easily see your suggested fate happening to them and the army falling into ambush.

Ok, what if the Romans have enough food to last a week to press to Saguntum once the harassment starts? They would be in battle formation, not in march formation like Lake Trasimene, so would be much less vulnerable. On the other hand, Cannae showed that battle formation can't save the day. Oops. But the battle of Trebia showed that the Romans could avoid annilation (albeit after suffering an embarrassing defeat).

If the Romans lose (either by the ambush you described or perhaps a pitched battle as I suggested), how do you think Saguntum surrenders? In OTL, they had nothing to bargin with when they ran out of food (heck, some believed the Romans were on their way and they only needed to hold out three more years with the food they don't have). In TTL, they know their aid failed them and the only thing they can bargain with is "well, you besieged us for 3 months and we held out another week before you killed our would be saviors, how about we submit to you, you not enslave us, and we don't drag this to 8 months?"

Since it's fairly likely the Romans would lose, what do you think about the Senate's plan for the war? Might they alter Publius Cornelius Scipio's orders and tell him to block Hannibal at Massalia? OK, the consuls technically call the shots, but usually when the Senate suggests a campaign goal they usually follow those requests and heir decisions include how many men, what to bring, which route, yadda. In the Punic Wars, the Romans never gave up, but the idea of re routing armies to places less likely to be defeated was not lost to them. Varro concluded the area around Cannae would be OK since Hannibal's previous victories used either rivers or hills to hide men. Cannae was flat, no possibility of ambush here. His plan was to use the numerical advantage to smash the enemy while friendly cavalry blocked enemy cavalry (the only unit that could thwart a more numbers= smash plan if the terrain can't hide troops). We all know how well that plan went.
 
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