After the Dragon War, King Galbatorix ordered the creation of a grand army to keep his newly-captured subjects in line. This army would grow and expand over the years until finally Galbatorix had one of the largest military forces in history.
The soldiers wore red tunics, with Galbatorix's symbol, a twisting flame, outlined in golden thread. Underneath the tunics, they wore leather brigandines riveted with squares of steel, mail shirts, and padded gambesons. The majority of the soldiers wielded broadswords, while the rest used bows and halberds. When fully marshaled, the strength reached sixteen thousand, excluding Urgals.
Role in Eragon
At the beginning of the Rider War, Galbatorix chose not to use his standard human soldiers, but an army of Urgals and Kull instead. The King appointed Durza the Shade to command the army. The army attacked Farthen Dûr in an attempt to destroy the Varden. However, after Durza was killed by Eragon, the Urgals were released from Galbatorix's control and the Varden won the Battle under Farthen Dûr.
Role in Eldest
After the loss of his Kull army, Galbatorix began to use his standard infantry. A platoon of these troops was sent to aid the Ra'zac in the Battle of Carvahall. Later, Galbatorix mustered all of his troops (he was able to muster a hundred thousand troops, filling the ranks of the Imperial army with mercenaries and conscripts) at Gil'ead and put them under the command of his new servant, Murtagh. The army attacked the Varden at the Battle of The Burning Plains. Thanks to the aid of the men of Carvahall, the Kull and Urgals of the Bolvek tribe and the dwarven army under King Hrothgar, the Varden were victorious once again.
Role in Brisingr
After Eragon killed the Ra'zac, Galbatorix sent his soldiers to search for him. Eragon first encountered six soldiers, but he was able to escape by turning invisible. Later, the presence of a company of soldiers forced him to enter the town of Eastcroft, where he met up with Arya. Still later, he and Arya ran in to fifteen soldiers. When the men tried to detain them, they were wiped out. The Imperial army also took part in the battles at Ceunon and Gil'ead.
The Soldiers With No Pain
Galbatorix invented a spell to make soldiers feel no pain. This would allow them to survive even the most horrendous of wounds. These were put to good use in Murtagh's raid, where 300 of them delayed the entire army of Kull, Orrin's cavalry, 200 swordsmen and 100 spearmen, killing many in the process. Later, they fought in one of the small battles that Roran was a part of and were defeated, even though they outnumbered the Varden troops. This proved that their strength was also their undoing. Their inability to feel pain caused them to ignore caution and even laugh when their limbs were sliced off, hence their name amongst the Varden, the "Laughing Dead".
Many soldiers were dispatched to defend supply trains for the army. One of these was attacked by Martland's command, including Roran, and defeated. Another group of undead soldiers was also defeated at a later battle. Galbatorix decided to take advantage of the Varden's absence from Surda by attacking with an army of about 700 soldiers, which was destroyed by Captain Edric's command of about 250 men, including Roran.
Lady Lorana sent out soldiers to slow the Varden's advance on Feinster. During the actual battle, soldiers from the Imperial Army fought alongside Feinster's citizens to defend the city. Here, too, they were overwhelmed.
The Imperial army was arguably the most powerful army in Alagaësia. Fully mustered, it was 16,000 strong and conscription increased its size to about 100,000 at the time of the Battle of The Burning Plains, excluding Urgals. Despite the overwhelming numerical superiority that the army enjoyed, it was far outclassed by the valor of the Varden and the strength of the Elves and Dwarves. At the Battle of The Burning Plains, the army was barely beating the Varden, which it outnumbered greatly, until the dwarves came, at which time it crumbled. Its numerical advantage was the only thing keeping the Imperial Army from being crushed and when it was faced with the superior strength of the elves or the numbers of the dwarves, it was greatly outclassed. This can be explained by the fact that soldiers who are torn from their homes will not fight as well as soldiers who volunteered, not to mention they probably had no training or experience at all and where likely to flee for any reason. The Laughing Dead and the Urgals where apparently more effective but they didn't make up a reasonable part of the troops to make a difference. However, the Imperial naval contingent was particularly effective with sloops patrolling the coastline of the Silver Sea. The Imperial flagship, the Dragon Wing, was stolen from the Blackmoor Shipping Company by Roran and Jeod in Eldest, weakening the Broddring Empire's naval capabilities.
In the Eragon film, the force that attacks Farthen Dûr was made up of both Urgals and humans. The Urgals entered first as expendable shock troops and then the Imperial Army arrived. In the book, there were no members of the Imperial army present.