The original Clone Army was a 3 million trooper order. Over three years, that contract with Kamino ran out. While these 3 million were the ultimate soldiers in the galaxy, there simply were not enough of them to keep up with demand. So the Republic contracted several other cloning firms, such as the Arkanian geneticists, and the Spaarti Cloning (Spaarti Clones could be vat grown and flash trained in a year, compared to ten for kamino).
The big problem with this, however, was that the Clones were only flash trained (think hypnotherapy), without the grueling training regimen at Kamino facilities. Arkanian Clones were created from Clone stock, rather than pure Jango DNA, which lead to degradation of quality over time and multiple cloning of clones.
The big thing though, was that these troops were not meant to be the perfect soldier, like the originals. They were meant to be an occupying force, winning through attrition and numbers, and being able to maintain an entire Galactic Empire.
The vast majority of Clone Trooper forces were not deployed until the Battle of Coruscant, where the currently overwhelmed 3 Million Clones and volunteer force suddenly got an influx of billions. These were housed secretly on Coruscant's moon, Centax II. With Coruscant breaking the back of the CIS armed forces, the Centax clones swarmed out through the galaxy, occupying it and paving the way for an Imperial takeover.
Thus, you get millions of crappy clones meant for security forces and Attrition wars, compared to the mobile strike force that was the Grand Army of the Republic.
The big problem with this, however, was that the Clones were only flash trained (think hypnotherapy), without the grueling training regimen at Kamino facilities. Arkanian Clones were created from Clone stock, rather than pure Jango DNA, which lead to degradation of quality over time and multiple cloning of clones.
The big thing though, was that these troops were not meant to be the perfect soldier, like the originals. They were meant to be an occupying force, winning through attrition and numbers, and being able to maintain an entire Galactic Empire.
The vast majority of Clone Trooper forces were not deployed until the Battle of Coruscant, where the currently overwhelmed 3 Million Clones and volunteer force suddenly got an influx of billions. These were housed secretly on Coruscant's moon, Centax II. With Coruscant breaking the back of the CIS armed forces, the Centax clones swarmed out through the galaxy, occupying it and paving the way for an Imperial takeover.
Thus, you get millions of crappy clones meant for security forces and Attrition wars, compared to the mobile strike force that was the Grand Army of the Republic.