The Old World was the southernmost land of the Great Barrier that separated the Old and New Worlds for three thousand years, before it was brought down by Richard Rahl.
The Old World was many times the size of the New World and its size a major contributor to the superior numbers of the army of the Imperial Order, when compared to the forces of the D'Haran Empire.
Comparison[]
By comparing the armies of The New World and The Old World as they were at their respective peaks we can determine some baseline for difference in size. The Old World would have to be at least 20 times larger in terms of population. The New World while taken into consideration leaves the amount of reinforcements Jagang's army was receiving. What is left out of consideration though is the amount of manpower needed for all the supplies the army needed as the plunder the army got wouldn't suffice to the amount such an army would need in the timespan the army was put into play. This number might also not be accurate due to the fact that most of the number Jagang's army is "volunteers" and perhaps Jagang would be able to conscript many times that number.
As stated in the books Sister Verna says The New World is but a speck on The Old World's back. Even including D'Hara as pointed out in conversation between Verna and Lieutenant Meiffert.
History of the Old World[]
The Old World was at the brink of a Revolution when Jagang with the support of Brother Narev established the Imperial Order and conquered the entire Old World. Jagang was a master of war he built Streets that connected the Old world and allowed his troops to react fast.