Spoiler Warning: this page contains detailed plot
Please note that the material in the following essay may not be the sole
explanation for the events we see take place in 1005 AD. There are other
probable hypotheses, but this seems to be the most logical as it reflects
some of the events of our own history, though on a much smaller scale. I
have included a great deal of speculation to support this hypothesis, but
as always read with a critical eye. Do keep in mind this solution is in no
way official according to Squaresoft.
During the time of Chrono Trigger we see Porre to be a small port town on the southern tip of the Zenan continent. It is rather difficult to judge just what the population of Porre was in 1000 AD but we can estimate. In all likelihood the town's population was rather small and was probably kept to under 10,000 residents. Considering the town was on a peninsula and was equipped to handle incoming ships (as evidenced by the numerous piers and wharves) it is likely the economy of Porre focused on fishing, tourism and freight. Do keep in mind this is only speculation, but was arrived at logically given the town's geographic setting. Much of the town's workforce probably operated in these three industries and relied upon trade with Truce. If this is true then it would be safe to say Porre had a stable economy.
It is important to note that we do not know if Porre is ultimately governed by Guardia or if it is a separate state. We know that Porre had its own mayor, but who does he report to? Given the fact that Porre ultimately overthrew Guardia, I have reasoned that Porre, as well as other villages on the outer continents, likely govern themselves and, for the most part, function independently of Guardia. And speaking of the Porrean mayor, we know that at the onset of Crono's adventure he was a very stubborn and greedy man. Though through changes made to the timeline's past, Crono inadvertently changed the mind set of the mayor's ancestors, thus turning him into a sharing and compassionate individual in the present. This, however, would not be enough to prevent the disaster that was waiting for Guardia.
With that point addressed, we can now look to Chrono Cross to help us piece together the information regarding Porre's rise to power. I would estimate that in the ninth century Porre began to build vessels worthy of sea travel. By the late 800's the ships were strong enough to survive a long-term ocean voyage. This is important because we are told by a Porre solider that around 900 AD people first began inhabiting El Nido. We know for a fact that the descendants of the Chronopolis workers had been thriving on the islands for nearly 10,000 years. So who are these people the solider was referring to? Quite simply, these were the sailors from Porre who had inadvertently stumbled upon the archipelago. A demi-human remarks that it was "humans from the continent" that had arrived in El Nido. I would like to stress that in the original Chrono Trigger timeline El Nido did not exist. Those sailors never stumbled upon the forbidden resources of the island chain and therefore Porre was able to build it's ports to become the modest seaside town described earlier. However, the sudden appearance of a new land mass would from here onward greatly alter Porre's history, the repercussions of which would affect the entire world.
These sailors had found both human and demi-human tribes living comfortably on the main island. Both groups lived together in harmony and shared in one another's culture. These native inhabitants were of course the descendants of the Chronopolis employees. We do not know what happened next, but it is logical to assume that the these sailors eventually returned to Porre to report their findings. The town then sent more ships to investigate this uncharted land. The leaders of Porre undoubtedly recognized the significance of this new world. Eventually more citizens traveled to El Nido whereupon the archipelago was designated a colony belonging to Porre. The port town of Termina was established to welcome Porrean ships and provide a home for the immigrants.
A demi-human states that "hordes of humans began to migrate to these islands and we were pushed into the outlying regions." It is unclear as to just where these "outlying regions" actually were. After the colonists established a settlement on the northern tip of the main island, the natives probably migrated south first (toward present-day Arni) before being pushed further away. Afterall, in 1020 AD Arni Village still has a very tribal look and feel to it where the residents practice a more primitive existence from those of Termina. It is possible these residents are the descendants of those natives forced to re-locate. However it is equally likely these outer regions came to be what is now Guldove and Marbule. In modern day El Nido some of the same rituals and lifestyles the natives had originally practiced can still be seen in Guldove.
Since El Nido had a strong connection to Porre we can assume both areas benefited from what the other had to offer. It is probable that more exotic foods and spices were present in the tropical archipelago that could not be found on the Zenan mainland. Crops useful for in textile manufacture probably grew in El Nido. Different minerals may have existed in the Fossil Valley that were foreign to Porre. We do not know exactly what goods were produced in El Nido, but we can be reasonably sure the colony traded resources with the mainland. Because of this Porre held a strong advantage in commerce that it could utilize while trading with Truce. As a result Porre's economy quickly strengthened and the town likely grew at an accelerated rate from what it would become in the original timeline. It is in this way El Nido began to shape Porre into a stronger force.
But wealth does not always beget might. It is important to note that in 1000 AD of this new timeline Porre had an elite military force. There was more in El Nido than just rare crops. The Dragonians who had been pulled over from their own timeline had occupied El Nido until the time of the colonist's arrival. Note that we do not know if it was the colonists who had irradiated the Dragonites or if they had become extinct beforehand. Regardless, the species left behind many valuable resources that were well beyond human comprehension. Some of which, like the Dragon Tear, were capable of DNA alteration. But what the colonists found interesting were the Elements. These were objects which utilized the power of the planet to bring forth powerful magic spells. Someone who was knowledgeable of how to use them could equip Elements and call forth fierce winds, lightning bolts, ice crystals, or ground tremors. Certainly unheard of on the mainland, the colonists were quick to export these priceless Elements to Porre. Additionally, we know that later in the tenth century mechanical wonders were unearthed in El Nido. Fort Dragonia was filled with manufactured devices from the future. Perhaps some of these were originally made for Chronopolis. Perhaps they were Dragonian in origin. Regardless, they were artifacts from a time far distant from the tenth century. This exposed the settlers to a higher form of technology than humans should have currently had. Since it was exclusive to Porre, it clearly gave them the advantage when they repaired the machines and implemented them into the armed forces.
Over the course of the next century the entire philosophy of Porre drastically
changed. As the village grew into a city we can safely assume different
individuals rose to power. It is entirely possible that the benevolent mayor
who once governed Porre in the present never came into a position of authority.
Instead, whatever group came to control Porre eventually saw fit to engage
in battle with Guardia. Maybe it was for the purposes of expansion, maybe
it was for greed, or maybe it was an act of revenge for an event that had
previously taken place which we are unaware of. Regardless, Porre had grown
in both size in power and possessed a military trained in the use of Elements
and advanced mechanical weaponry.