Bucellarius

Overall strategy
The Bucellarius is the backbone of the Roman cavalry arm, and consists primarily of a man clad in armour and trained to fight as sword cavalry. Unlike Scout Cavalry, he usually tends to have a better mount, and has some body armour, so he can be relied on to lead the charge in combat. Of course, his accoutrements make him a bit more expensive but what you see is what you get., Bucellarii are best used in the early game as your primary shock cavalry force, until other units such as the Athanatoi and the Scholae make their appearance.

Background
The bucellarii were the military elite of their day, fighting battles from the Euphrates to the Atlas Mountains, and from the Sahara to the Alps. Generals of the later Roman empire were allowed (and perhaps even encouraged, as a cost-saving measure to the Imperial treasury) to raise private regiments of bodyguard cavalry, paid out of their own purse. These troopers were called bucellarii.

This Latin term meant “Biscuit–Eaters”, though perhaps a better translation might be “hardtack eaters”; referring to the soldier’s campaign rations of hard-baked biscuits (known later in history as “hardtack“). These private regiments could number as few as a single bandon (a 200-300 strong tactical unit of the late Roman and early Byzantine armies), or (in rare cases) as large as a tourma/turma (a division in the Byzantine army, varying in size from 3,000-4,000 men). The largest and best known of these was the bucellarii of Belisarius, in the mid-6th century, which numbered 7,000 at its peak.

Bucellarii began as a single 300 man bandon formed by Belisarius as an experimental unit; this under the sanction of the Emperor Justin while Belisarius was still a young, promising officer of the Guards in Constantinople. Unlike most Roman cavalry of the day, who were either lancers or horse-archers (Hippo-toxotai), Belisarius trained these men in both roles. Every trooper was armored as a heavy cavalryman of the day: with helmet, cuirass, greaves on their shins and vambraces protecting their lower arms. All were armed with lance (kontarion) and sword (spatha), for use in close-quarter combat. They were also equipped with the powerful Hunnish composite bow and could use this deadly weapon on the gallop almost as well as the Huns themselves. Finally, they had a brace of lead-weighted throwing darts, called plumbatae, attached to the front of their saddle. These latter were deadly when thrown at close range, further augmenting the fire-power these horsemen could bring to bear in a melee.