There were several USG offices in the Twin Towers, some of them intelligence. In addition, CIA was located in 7 WTC, along with Secret Service and military offices. The military offices were used as cover for the others. There was far more USG in WTC than in Murrah, and the lesson learned in OKC was no doubt useful to the attackers: collateral hurt to innocents is magnitudes more powerful than hitting military targets -- that is what strategic bombing was invented to demonstrate, not to say threatening with WMDs, a practice invented by the US and which remains its primary defense strategy. The cause and effect between USG WMD threats and terrorist attacks is yet to be fully admitted outside military circles: the military accepts that innocents will be slaughtered, and the winner must slaughter the most. Terrorism to the military is a nuisance even when a few of its troops are picked off. The losses in Iraq do not even make a blip on expected casualties of a major war. More military have died in conventional accidents, murders and suicides around the world than have died in Iraq and Afghanistan. But those in the Middle East have greater utility for the military to boost its suck for more funds and more "our boys and girls" sacrifice and more bawling in congress and the presidential campaign about protecting the nation, defense cut-back not even a dream since ever so convienent 9/11. Murrah bombing helped the battle against homeland militants, and WTC got the ball rolling for battle overseas. Who planned them is yet to be revealed, but the usual suspects don't mean shit.