After a few years at Stokeham, Casca has to leave as he always must, and travels to Sicily where the Normans under Robert Guiscard are carving out a kingdom.  Casca offers his services as a mercenary and fights the Saracens and locals, until news of a disastrous defeat in the Byzantine army pulls him across to the fading Empire and he meets the general Alexius Comnenus.  Impressed by his ability, he becomes a trusted lieutenant and they overcome rival factions to put Alexius on the throne.  Casca then leaves to the east.

Casca is captured by Muslim slavers and takes the name Kasim the Spear after helping to defeat bandits.  While en route to Baghdad where he was due to be sold, he is taken to Castle Alamut, home of the Assassins, and inducted into the cult through the use of drugs.  Sent to kill under the orders of Hasan al-Sabah, Casca makes a mess of things and is taken prisoner.  He is rescued however and finally joins the company of Persian poet Omar Khayyam and vows to go with him north to the lands of the Rus.

Lost in a sandstorm, casca eventually returns to Byzantium where the Emperor tells him a crusade is on the way and he is to join it and spy on the crusaders.  Helping to take Nicea from the Turks, Casca becomes a part of the crusade to Antioch and then Jerusalem, but the slaughter by the crusaders on the people of the city sickens him and he departs.

He finds a village in Asia to settle in for a while, helpign them to defeat a local wearlord who has been terrorizing them, but he moves on in time and makes his way to Chin.  Here, the warlike tribes to the north, the Jurchen, capture Casca and eventually he becomes one fo their number, invading the lands of Chin and conquering it.  Then he becomes involved in the war against the Southern Sung across the great river, hiring himself out as a mercenary to which side wishes his services.  Finally he's hired by a merchant to escort his goods by sea but he is shipwrecked.

Washed ashore on Japan, Casca teams up with Japanese warrior Jinto Muramasa, who is on the run from the Taira, one of two competing dynasties in a war.  The two travel north to the castle of the Minamoto and join the army to fight in the civil war.  After a bloody campaign, both are created Samurai at the climactic Battle of Dan-No-Ura, but Casca is condemned to death for trying to stop the murder of the boy Emperor.  Jinto suggests Casca is tied to a broken mast and set out to sea, which the Minamoto agree to.

In Casca 20: Soldier of Gideon, Casca is referred to as being in Jerusalem in 1187 when Saladin conquered the city.

Picked up by a trader, Casca is set ashore in India and makes his way to the Holy Land where he has heard of a new warlord and leader, Saladin.  Casca rescues a young woman and her father from the clutches of Reynauld of Chatillon, a crusader lord, but Casca is thrown off the walls of the castle as a result.  Vowing revenge, Casca joins Saladin's army and is victorious at the Battle of Hattin - and he also kills Chatillon.  Part of the conquering army that takes Jerusalem, Casca then falls foul of intrigue and is sent north to a border patrol where he is taken prisoner and sent to Samarkand for selling in the slave market.

Fighting as a chained beast in arenas, Casca is rescued by a young Mongol called Temujin.  Casca readily agrees to help the young man in his quest to regain his place in his tribe, and the two slowly build an army, Temujin learning how to fight wars from the teacher Casca.  Temujin takes a wife and dominates the tribes he conquers, forming them into a vast army.  Victorious at the deciding Battle of Baljuna, Temujin is shortly afterwards proclaimed Genghis Khan - Great Leader - and begins to build an empire.  His work done, Casca decides to leave.

Crossing over into India, Casca is captured by soldiers of the Delhi Sultanate and taken to the capital where he is made into a personal slave of the Sultan.  Proving his prowess in battle, Casca is enrolled into the Sultan's army and rises in rank, although still a slave, until he is commander of the Palace Guard.  When the Sultan dies, the successor his daughter Raziya, takes a dislike to him and Casca flees, pursued by soldiers loyal to her.

Rescued by Mongol scouts, Casca is taken to Subutei, a general who knew Casca when Genghis Khan was alive.  Now the Khan is Genghis' son and orders have been sent out to conquer Europe, so Casca joins the invading army as it rides through Russia and Poland, spreading destruction.  Casca goes with the southern branch and helps the Mongols defeat the Hungarians.  But news arrives of the Khan's death, and as the Mongols retreat, Casca slips away south to the Byzantine Empire.

The Empire is fragmented and in disarray, but Casca helps the general Michael Palaeologus gain the title of Emperor and they retake the lands lost to the Latins and rival Byzantine forces, and ultimately the capital Constantinople.  In the celebrations Casca leaves, recognizing the Empire is not strong enough to survive long.

Finding his way to the troubled Holy Land, he hires himself out as a hired sword but tires of the squabbling amongst the remaining Crusader lords and travels to Venice. 

In Venice Casca saves the life of young Marco Polo and becomes embroiled in his family politics.  Marco's father returns after years of being away and they set out with Casca and a few friends eastwards to the lands of the Mongol Emperor Khubilai Khan in China.  While there Casca helps thwart a coup and win a war for the Emperor.  When the Polos return to Venice Casca goes with them.

Some of the following is mentioned in Casca 24: The Defiant, and in Casca 21: Trench Soldier Casca is referred to as fighting at the Battle of Agincourt in 1415.

Casca travels through Europe, stopping in an Alpine village but plague drives him away.  Making his way to Scotland he fights against the invading English under William Wallace but when the war turns against the Scots Casca is forced into hiding.  Hunted by superstitious Scots and the Brotherhood, Casca's escape is helped from an unexpected source.  He ends up in Wales and trains as a longbowman and when war with France comes Casca joins up as an archer and helps Edward III win at Crecy.  With war petering out, Casca departs and has some time in the far north whaling and fishing. 

When his friends grow old or die Casca returns to warmer climes and finds the Byzantine Empire disintegrating under Ottoman Turkish invasions.  Fleeing with refugees to Constantinople Casca is recruited by the Emperor and his Court to recruit the assistance of a power that can defeat the Turks.  A Mongol speaker, he's sent to the Golden Horde but the Horde is engulfed in civil war.  Travelling to Central Asia he finds a new warlord called Tamerlane who's buildign an Empire.  Assisting him in building up a mighty army, finally after many campaigns Casca persuades Tamerlane to turn on the Turks and at Ankara in 1402 smash the Ottomans.  But the Empire is too weak to recover.

Ending up in England Casca takes part in the invasion fo France as part of Henry V's army and wins a victory at Agincourt.  When the campaign ends Casca moves on and comes to Italy, hiring himself out as a mercenary to the city states.  Mostly he fights for Genoa but tires of it and comes to Portugal where a ship is ready to sail into the unknown.

The ship, The Kuta, is sunk by pirates and Casca spends a few years at the bottom of the sea.  When he's pulled up by fishermen, he is mistaken for Olokun, a god.  They want him to free them frfom a despotic king, Awanoshe.  When Casca reaches the capital he witnesses brutal torture and the madness of Awanoshe is evident.  But Casca, as a god, is taken on by Awanoshe and goes with the army to conquer a neighbouring kingdom.  But Awanoshe works to destroy Casca's reputation and when the army is deliberately allowed to lose, the king turns on Casca.  Backed by senior army generals as well as the population, Casca leads a coup that deposes Awanoshe and installs his brother Ewuare on the throne. 

Returning from Africa, Casca makes his way to Italy and learns that the Turks are preparing to conquer Constantinople.  Joining up to help defend the city from overhwelming odds, he fights for the last city of the Caesars until sheer weight of numbers overwhelms the Graeco-Italian defenders.

Wounded in spirit by the death of the last link to the Roman Empire, Casca wanders through Germany, stopping to talk to Johannes Gutenberg.  Hiring out his sword to the Duke of Burgundy, he is then recruited by the Duke of Somerset to fight for the Lancastrian faction in the English civil war against the Yorkist faction.  The war lasts 30 years until the final Battle of Bosworth where the last Yorkist leader, King Richard III, is killed.