Queen Michael said:
When ep. IV-VI take place, ordinary people (non-clone humans, that is) were allowed to join the stormtroopera. The Jedi clone army was clone-exclusive.
From sources like Star Wars: Jedi Starfighter and Nomad, and even through various Star Wars: Republic comics and the novels Labyrinth of Evil and Jedi Trial, there are several instances before and after the Battle of Geonosis showing non-clone soldiers serving as the majority of forces in military conflicts and being actively recruited by various military organizations. The reliability and quality of mercenaries and bounty hunters would not be high, and having large numbers of non-clone troops available from the outset of the war would have eliminated the need for a clone army and ended/prevented the controversy over the Military Creation Act. It should also be stated that the sources that depict non-clone forces prior to Geonosis are all referring to small-scale conflicts and minor battles.
Additionally, the non-clone military forces in the Battle of Praesitlyn in Jedi Trial were largely non-Republic mercenary forces. The Sons and Daughters of Freedom mercenary group, which contained 50,000 infantry troops and thousands more serving as armored unit and starship crew members, had its number of active members reduced to fewer than 2,000 operatives by the end of the battle. Moreover, the non-clone Praesitlyn Defense Force is entirely wiped out by the droid invasion force, with its own commander stating that non-clones are far capable at combating battle droids. Likewise, while the Republic force sent to Praesitlyn consisted of only 20,000 clones, as well as additional non-clones, the only non-clones described in the novel are member of either the command staff, starship crews, or support personnel. When that force faced off against the Separatist force of over one million droids, the clones took extremely heavy casualties and would have lost the battle had it not been for two successful suicide missions undertaken by the commanding Jedi General against the Separatist leadership.
Megalodon said:
And (Ewoks excepted, becuase fuck Ewoks),
The Ewoks won because of he element of surprise, in a way. When occupying Endor's moon, they simply left the Ewok's alone, thinking that they were no threat.
"We can safely ignore these contemptible little fur-balls."
―Captain Toss, Imperial Survey Team IX3244-B
However, a botched attempt at first contact with Ewoks by some Imperial soldiers resulted in Ewoks terrorizing Imperial positions. Still, the Ewok's were ignored. Then, they launched a surprise ambush on the imperial position at the shield generator. Although initially surprised by the ambush, Tempest Force regained the upper hand and squads of Stormtroopers pursued the Ewoks into the forest. Despite being outnumbered by the natives, the Stormtroopers with their armor and advanced weapons forced the Ewoks back, and Imperial AT-ST scout walkers decimated Ewok holdouts. The Ewoks tried, but were unsuccessful with a number of tactics, such as using gliders to drop stones on top of the walkers, and trying to trip them with ropes.