But Mace and Company didn't go planning to kill Palpatine. They went in to arrest Palpatine. Only after Palpatine began fighting did Mace change his mind and decide to assassinate him. They spent maybe five minutes coming up with an arrest plan, it failed, and Palpatine killed the lot of them. They failed because they were using the law enforcement method -- utilize the minimum amount of force and take your target alive, with minimum injuries.

This has no bearing on Obi-wan and Yoda's failure to come up with a viable assassination plan over the next month, year, or 20 years. Obi-wan and Yoda knew that the law enforcement method wouldn't work, so they could use the military method -- utilize as much force as necessary to neutralize your opponent as quickly as possible. We know the Emperor left Coruscant -- the Jedi could've struck at his shuttle or his Star Destroyer. We know the Jedi could enter the Imperial Capitol with impunity -- they could've gone back and caught him unawares, or booby-trapped his office. We know the Emperor surrounded himself with armed guards and courtiers -- the Jedi could've infiltrated them. The surviving Jedi could've marshalled their resources to strike against their enemy; they really only needed to get two targets, since the deaths of the Emperor and Vader inexorably led to the attrition of the Empire down to the Remnant.

But they didn't do any of those things. Yoda lost one fight -- really a ritualized duel -- and went into comfortable retirement while Palpatine inflicted unprecedented depredations on the galaxy. Can you imagine if modern wars were fought like that? George W. Bush would sneak into Osama bin Laden's headquarters and they'd have a fistfight. George played rugby and keeps in pretty good shape, but Osama's got reach on him. Let's ignore the purported kidney problems and say Osama knocks George down. Doesn't kill him, doesn't even capture him or wound him, just knocks him down. Then George runs away, "Ah've gotta go inta exile back on ma ranch," and Osama bin Laden takes over the United States and puts all our women in burkas. On his way to Crawford, George runs into Dick Cheney, fresh from maiming and burning alive Abu Musab al Zarqawi. They decide that Osama is too powerful to fight, so Dick is going to go into exile, too. Pretty ridiculous, right? That's how the Sidious-Yoda confrontation turned out. Yoda was *knocked down* and he gave up ran away. "Wars not make one great." Losing a duel and running away makes one great.