Sifo-Dyas was a loyal Jedi Master, and leading member of the Jedi council. He was, however, of like mind as Qui-Gon Jinn and Count Dooku(who was still a Jedi at the time), meaning he was a free spirit, willing to bend the rules if he thought it was in the best interest of the Jedi and Republic as a whole. Master Sifo-Dyas felt the Jedi's power slowly deminishing, as Yoda and Mace spoke of in ep II, and knew what it meant: the darkside, and the Sith, were growing in power, and that meant there would be a comming war.

another interesting note about Dyas that is seen in the visonaries comic is that Dukoo uses some of the blood from the fallen Jedi (who he keeps in some type of crigenic suspesion) in a transfussion to bring general grevious back to life.

He knew the Jedi might not be able to defeat them alone, for one reason because the Sith had been planning their assault on the Jedi for the past thousand years, as well as the Sith would have the advantage of first attack(since the Jedi did not know who or where they were) and felt the Republic would need an army to survive. He also knew the council wouldnt allow the creation of such an army without proper justification, but he knew they wouldnt have proper justification until it was too late. For that reason he ordered the army in secret, so that there would be an army which could be called upon when the Sith finaly did show themselves, and one that the Sith did not know about or expect, since it was being made in secret.

However, at the same time, Qui-Gon Jinn(who was a close friend of Count Dooku, as he had been his padawan) was suddenly killed, deeply affecting the Count. Dooku had also grown to the point of disgust with the corruption in the senate which controled the very republic the Jedi were sworn to serve. If the senate which controlled the republic was corrupt, and the jedi served that republic, did that not mean the Jedi were serving a corrupt entity, and therefore corrupting themselves?

It was for these reasons Dooku felt he could no longer serve the Jedi Order. Dooku considered seeking out the Sith Lord who he was convinced did exist and was causing the dark side to grow more powerful, until it was he who was sought out by Sidious. Dooku listened to what Sidious had to say, and became convinced that Sidious did in fact want to create a new Empire that wasnt corrupt, like the Republic the Jedi now served, while at the same time becomming corrupted himself by the power Sidious promised. Sidious would use the clone army for his own agenda, that being to destroy all other armies which could even stand up to him, and more importantly, the greatest thread to his plans, the Jedi Order.

But, since Sifo-Dyas was a loyal Jedi, and was behind the whole clone army creation, he would have to be killed if the clone army was to be used for another purpose. Sifo-Dyas was mysteriously killed, or at least mysteriously to the Jedi Order, when in actuality it was his former friend, Count Dooku, who murdered him. In doing what Sidious required of him, gaining control of the army Sifo-Dyas had ordered, which would ultimately be used in his master's grand plan, Dooku had one more task to complete before he could truly become Sidious's apprentice. Dooku then deleted Kamino from the Jedi archives to ensure no-one came across the army until he and his master were ready for the army to be used, and officialy left the Jedi Order.

The next step was to defeat all armies which could stand against Sidious in the future. Dooku disappeared for years. He re-emerged the leader of the Seperatist movement, composed of all the major armies of the galaxy(the trade federation, the intergalactic banking clan, etc), which sought to forcefully remove themselves from the Republic. This gave the chancellor the excuse to form an army of his own to defend the republic against this threat.

Obi-Wan was led to Kamino at just the time the Republic needed said army. Although she didnt know it, Zam Wesell was never intended to suceed in her assassination attempt on Padme. Sidious, Dooku, and Jango knew that Zam wasnt powerful or skilled enough to kill someone under the guard of the famous Obi-Wan Kenobi and Anakin Skywalker. They knew she would fail, and would be captured. But they wanted her to be captured so Jango could then kill her, and in doing so place the evidence needed to lead the Jedi to the clone army.

Jango Fett purposely used a strange type of dart(which was really a clue) lead Obi-Wan to search for its origin, which he found missing from the jedi archives, then compelling him to go to the planet Kamino and discovered the clone army at the precise time Sidious wanted the army to be found so he could use it. The republic had their army, the seperatists had theirs and they finally went to war. Dooku, secretly serving the leader of the Republic(and dark lord of the Sith), knew that the Republic had to win, and manuevered events little by little in the Republics favor, ensuring they won the war. When the war was at its end, the Seperatist made one final, desperate attempt at victory by attacking the capital of the republic itself, and 'capturing' it's chancellor. Obi-Wan and Anakin rescued the chancellor, killing Dooku in the process. After the Seperatists were defeated, and there existed no armies which could stand against Sidious when he took over, the last remaining enemy was the Jedi Order itself.

Ever since being told by Dooku that a Sith lord was in control of the senate, the jedi, though timid at first, began to look closer and closer and the senate. Finaly the Jedi realized who was orchestrating the entire thing, and that the supreme chancellor was really the Sith lord Dooku had spoke of being in control of the senate in ep II. What they did not know, however, was that Sidious instructed Dooku to tell them about a Sith lord controlling the senate. He knew the Jedi were no fools, and would eventualy find out it was him. He also knew that when they did, they would try to destroy him, which would look as if the Jedi order, was now trying to assassinate the supreme chancellor of the republic, and were traitors. He also knew that, suspecting him to be a Sith lord, the Jedi would send some of its most powerful warriors to arrest him, and he also knew that these warriors would include several members of the Jedi council, whose actions represent the entire Order.

They went to arrest him but were unsucessful, and to the senate and republic it looked like the Jedi had tried to assassinate their supreme chancellor(when in actuality, they only fought him because he attacked THEM), who was a hero in their eyes, as he had won the war against the seperatist, insuring the saftey of the republic. The Jedi Order, which had served the Republic faithfully for 10,000 years, was declared an enemy of the Republic, for alledged treason, and the order was destroyed by the clone army, led by former Jedi Anakin, completing Sidious's master plan which spanned decades.