Wanted to give some historical insights on the Sicilian civ bonuses.
Civilization bonuses
Castles and Town Centers are constructed 100% faster.
Land military units absorb 50% of all incoming bonus damage.
Farm upgrades provide +100% additional food to Farms before they need to be reseeded.
Can build Donjons, which replace the regular Watch Tower line.
Team bonus
Transport Ships +5 carry capacity and +10 armor versus anti-ship bonus damage.
Castles and Town Centers are constructed 100% faster.
Faster building Castles/Town Centers reflects the Norman penchant for castle building. While famous for building castles in England, the Normans also constructed many throughout Southern Italy and Sicily, such as the Castello Normanno (“Norman Castle”) in Aci Castello, Sicily (built impressively on a rocky outcrop facing the sea) or the Castle of Melfi in Melfi, Italy. There are several castles and towers in the region referred to as “Norman Castle” or “Norman Tower” in Italian, reflecting the ubiquity of these constructions during the relatively brief period of Norman rule.
In fact, this period of Norman Italy/Sicily (11th and 12th centuries) was known for incastellamento (encastellation), as castles sprung up so rapidly. Castles gave the Norman elite – always relatively few in numbers – the ability to control territory and manage very large and diverse subject populations, especially in Sicily. Castles and simple keeps or donjons also provided effective defense against feuds with Norman families (such as the conflicts between the Hautevilles and Drengots) and other invading powers. Castles also served an almost-offensive component, as represented by Count Roger’s conquest of Sicily which was made possible by his gradual expansion out from his power bases of castles and towers.
In fact, the geography of Southern Italy and Sicily, with its mountain ranges and narrow coastal plains, encouraged the construction of castles as a means to control and defend key terrain such as valleys and coastal cities.
Land military units absorb 50% of all incoming bonus damage.
During their height, the Normans (and especially their cavalry) were militarily unstoppable on the battlefields of Southern Italy, the Balkans, and the Near East, such as at the Battle of Dyrrhachium (1081) when the Normans broke the center of the Byzantine lines with a direct charge. The Normans would have similar successes in direct melee with Arabs, Berbers, and Turks despite often being outnumbered. For example, at the Battle of Cerami (1063), a little more than 100 Norman knights decisively defeated a much larger Arab/Berber force, estimated in the thousands, through direct cavalry charge. Simply put, the Normans did not have a lot of tactical tricks up their sleeves to make up for their small numbers, but could still win with sheer ferocity.
In addition, this bonus reflects the Italo-Norman success against their enemies. Similar to how the Lithuanian Leitis – with an attack that ignores armor – is especially effective against Teutonic Knights and Boyars, the unique units of two civilizations the historical Lithuanians fought and had successes against, the Sicilians being able to mitigate bonus damage reflects the Sicilian/Norman successes against their historical opponents: the Byzantines (with their anti-infantry Cataphracts and their other counter units – spearmen/skirmishers) and Saracens (camels).
Farm upgrades provide +100% additional food to Farms before they need to be reseeded.
Dating back to Roman times, Southern Italy and Sicily has always been an agricultural center, owing to its warm climate and the fertile volcanic soil in the region. The Roman latifundia, or large farming estates, were long a feature of Sicily into the Middle Ages. While some historians suggest that the persistence of latifundia had long-term negative effects on the development of the Sicilian economy, the bonus makes sense when one considers that these large estates would have contained significant agricultural area – hence the increased amount of food for a given farm.
Can build Donjons, which replace the regular Watch Tower line.
The design of the Donjon itself is based on the Castello di Adrano in Adrano, Sicily (built in 1072 by Count Roger I of Sicily) – which features a square tower above a recognizable larger base, possibly built up over an older Arab structure. Count Roger is believed to have erected this tower as a fortified outpost to assist in his conquest of the nearby city of Catania. The Normans often used such structures as bases of operation for offensive actions throughout a region. This history of offensive building is also reflected in the fact that the Donjon can train Serjeants and Serjeants themselves can build Donjons. In the game, the high armor value of the Serjeants allows them to hold their own in hostile territory a bit longer than regular infantry can until players can send in their Knights from their main bases.
Transport Ships +5 carry capacity and +10 armor versus anti-ship bonus damage.
The Italo-Normans were not particularly effective at naval combat – as evidenced by a number of naval defeats against the Byzantine/Venetians – notably, the Battle of Corfu in 1084. They were, however, extremely innovative at transporting armies and horses, as well as undertaking amphibious operations, most notably in their initial conquests in Sicily as well as later in the Balkans. For example, in May 1061, Roger crossed the Strait of Messina separating Italy and Sicily with a surprise night-time crossing while the city of Palermo was taken 11 years later by an amphibious invasion. Transports having additional carry capacity and armor reflects this Norman/Sicilian ability to strike out via sea.
Overall
While the Italo-Normans were relatively few in numbers, they showed impressive ability to strike quickly into, seize, and control disparate areas, as reflected by their pretty wide territorial range (also seen in the Hautevilles campaign). The combination of the Transport Ship Team Bonus, the Donjon, the Serjeant, and the faster-building Castles reflects this history as it gives the Sicilian player ways to strike out on both land and sea and hold territory for follow-on forces. The ability to ignore bonus damage reflects their sheer military dominance throughout the 11th and 12th centuries.