Modern maneuver warfare follows a basic Sun Tzu principle from the Art of War:Things are getting worse in Afghanistan and Pakistan not because our attention was elsewhere, but because AL Qaeda has been driven from the Arab world, with nowhere else to go.
Al Qaeda isn't fighting to revive the Caliphate these days. It's fighting for its life
In the battle for Iraq, the United States military used a classic strategy in maneuver warfare: feint and attack.
If we wish to fight, the enemy can be forced to an engagement even though he be sheltered behind a high rampart and a deep ditch. All we need do is attack some other place that he will be obliged to relieve.- Sun Tzu

The original plan had called for a classic pincer movement, attacking from two directions. The 4th ID was going to come from the north, through Turkey, while the main force attacked from the south. When Turkey decided against allowing these forces in, the battle plan had to change. The threat of the 4 ID coming from the north, presented as ongoing public negotiations, kept certain Republican Guard elements from massing against the smaller American forces in the south. They stayed in the north to defend that potential passageway. Turning a pincer movement into a feint and attack.
In the south, another strategy had to be worked in order to further divide the strong Iraqi forces. That was worked as a "feint and attack" within the larger feint. By feinting to the east with a much smaller force, as if to do a flanking maneuver around Baghdad to cut it off, it forced other Republican Guard heavy armor units to stay in place. Where they were attacked by air power. The larger ground force drove straight through to Baghdad.
In Afghanistan, bin Laden's organization had deep connections within the many tribes of Afghanistan, particularly in the Pashtun tribal areas around the Pakistan border. These connections went back to the Afghan/Russo war, 1978-1989. At the time, bin Laden was only one of many leaders of the "mujihadeen". Towards the end of the conflict, he had managed to organize a number of smaller groups into a slightly larger, though loose, confederation of fighters. This allowed them to develop better strategic control and tactical capabilities while maintaining their best offensive guerrilla tactics of hit and run attacks before egressing back to relatively protected enclaves in the Pashtun tribal areas and even further back into Pakistan.
When the war was over, bin Laden not only maintained his many contacts within the tribes, but with various leaders and organizations that still existed to one degree or another. When the Afghan Civil War began in 1990, bin Laden supported the Tali-ban fundamentalists in their bid to control Afghanistan. The civil war eventually ground to an armed stalemate in 1996 with the Tali-ban controlling major population centers like Kabul and Kandahar while the Northern Alliance was largely restrained to the north. The Tali-ban, being largely drawn from the Pashtun tribes from both sides of the Afghan/Pakistan border, and, by extension of tribal protection, bin Laden, enjoyed both support and protection.
This protection was not solely related to these tribal affiliations. The geographic features of Afghanistan had long offered natural defenses. High mountains acted as defensive walls around protected valleys that had been more or less self-sufficient for centuries. It was these natural defenses and tribal affiliations that the mujihadeen had used so effectively against the Russians. They learned the many passageways and protected hides. They had established fortified compounds and underground caves and passages.
This gave bin Laden and AL Qaeda a definite advantage if attacked. He planned to use this knowledge of the terrain and relations with the people to defeat the United States in the same way that he believed the Russians had been defeated in the '80's. He expected that, after attacking the United States on a massive scale, it would be forced to attack. He knew that the United States' war doctrine was to use overwhelming power to flood the area and destroy the enemy.
He believed that the United States was wedded to this doctrine based on the military history of massed warfare from its origins through Viet Nam and its massing of troops along the Fulda Gap to repel the potential massive attack of Soviet forces. This defense was aligned against the Soviets even in the face of massive nuclear strikes that seemed to make these massed forces redundant if not obsolete. This insistence on overwhelming fire power seemed to culminate in the United States massing 450,000 troops to expel Saddam's Iraqi Army from Kuwait.
Bin Laden expected the United States to send massive numbers of troops to Afghanistan. He expected to use the terrain, his advantageous knowledge of of passages and fortified areas and his relationships with the tribes the same way that he the mujihadeen had used them against the Russians two decades before. The same tactics that Afghan natives had been using against invaders for centuries. In short, to tie down significant American forces in a long drawn out war of attrition that would be costly in money, material and casualties. He believed that the appropriate lessons in battling massed forces came from the Afghan/Russo war and the United States war in Viet Nam.
Bin Laden also expected to mitigate United States air power through similar traditional means. First, by hiding among the population making extensive use of air power dangerous. Collateral damage sways both international opinion and local allegiances. Second, by forcing the expenditure of money and time on expensive munitions, fuel and equipment. Finally, by hiding in caves and other hard to locate areas, it would take greater time to track and attack with little overall effect. Of course, there was also the mujihadeen's previous success against Russian helicopter gunships and fighters using rocket propelled grenades and MAN-PADS. What bin Laden may have underestimated or failed to appreciate was the significant advancement in precise munitions such as laser guided JDAMS, smaller, but lethal warheads and "Daisy Cutters".
His other strategies included attempting to dislodge American influence and protection from Saudi Arabia and other parts of the Middle East. He announced his opposition to the governments of these nations in 1998 by calling them corrupt and in bed with the "infidel" that meant to eradicate the Islamic Umma. He orchestrated various attacks on Western targets in the Middle East. When he attacked the United States on September 11, 2001, most of the men were Saudi Arabians. On the outside, he may have hoped to provoke the United States into attacking in the Middle East, specifically, Saudi Arabia, but it was likely not an expected outcome.
While many focus on this hoped for outcome, it would seem out of character for someone to carefully consider each move and expectation to believe that such an obvious ploy would have had such a definitive effect. Feasibly, he probably hoped to at least cause a rift between the US and these governments and promote some support within the Muslim world proper. It is not incorrect to surmise that Bin Laden was hoping for such an attack to occur, but it is oversimplified to believe that it was his primary plan. Particularly because he had not put much effort in building significant armed forces in Saudi Arabia or other Middle East nations.
For all of bin Laden's purported networks and influence, his weakest support and direct combat forces were in the Middle East. While his attack on the US may have motivated some sympathy within the Middle East, it also caused some revulsion and rejection. Further, there were really no countries in the Middle East where bin Laden and other groups could freely coalesce, organize and train enough forces to mount a direct rebellion or outright attacks on the United States or government forces without being identified and interdicted. Militarily, he had few resources. His networks were monitored and infiltrated. In the end, most of bin Laden's immediate military capabilities were in Afghanistan and Waziristan, Pakistan. His networks in the Middle East were largely set up to funnel fighters, materials and money to that front.
Alternately, such an invasion on the part of the United States would have been a complete and horrific blunder. Not only would it have provoked exactly the response that bin Laden would hope for, but it would have likely resulted in an immediate global crisis when Saudi and Gulf oil was interrupted.
In planning a military response to the September 11 attacks, the United States had to take into consideration two important points: global impact and the history of warfare in Afghanistan. Attacking bin Laden directly, confining the fight to Afghanistan and allowing bin Laden the benefit of his established fortified positions was a sure way to end up exactly where the Russians had in '89: broken and in retreat. Bin Laden was counting on that. Not because it would have given him new territory, but because it would have solidified his position as the defeater of a world power and a leader, by right of military victory, of the Islamic Umma. The strong horse. However much bin Laden had tried to claim a victory over the Russians, it was tainted by the support that everyone believed he and the mujihadeen had received from the United States. It is one of the reasons that Zawahiri had written in "Knights Under the Prophet's Banner" that bin Laden had not received any assistance. They needed to separate themselves from the same taint that they insisted was on the other Islamic governments.
The United States sought to avoid that trap by first limiting the number of forces that it would commit to the country. These forces were already limited in size and equipment by the terrain and routes of ingress and egress. Supply and defense of routes would be difficult. Smaller forces also meant not taking control of all of the Afghan territory. That meant having to rely on an alliance with local warlords who were either neutral or in open rebellion against the Tali-ban.
It also meant that the US would have to rely on small forces to track and attack bin Laden and the Tali-ban. In fact, this was one tactic that the Russians had used effectively against the mujihadeen in the earlier war. Small groups of Spetsnaz (Special Forces) would walk into the mountains and fight straight on battles with the small groups of mujihadeen, who were concentrated that way to avoid detection by larger Russian forces, that would either attempt to ambush or be lured into a counter ambush where helicopter gunships could be used (depending on the altitude) like cavalry. The mujihadeen countered by moving higher into the mountains where the helicopters were unable to fly due to engineering limitations. The terrain also presented dangers to helicopters and men alike. This was compounded by the provision of RPGs and MANPADs that the mujihadeen incorporated into their tactics. Jet Fighters in the eighties did not have the precise munitions as they do today which meant that their contributions would also be limited.
However, technological advancements provided the US with some advantages the Russians did not have. Helicopters could fly longer and higher. Stand off, laser guided munitions improved the use of high flying bombers and fighters, reducing reliance on helicopters that were vulnerable at high altitudes and to mujihadeen tactics. The United States also used their alliances to increase their force on the ground.
Bin Laden and the Tali-ban had been forced to retreat to Tora Bora. US forces with local and some international allies special forces are widely believed to have had bin Laden and contingent of about 1,000 fighters held up in the mountains in December 2001. Unfortunately, these forces negotiated a truce with the local allies against US advice. While the negotiations continued, captured fighters reported that bin Laden and others had slipped away over the White Mountains into Pakistan while the remaining fighters conducted a rearguard action to distract the US and its allies.
Pakistan is a sovereign nation with a large military and nuclear weapons. The United States had negotiated with Pakistan for a supply route and to stop supporting the Tali-ban directly. The Federally administered tribal area (FATA) was a simmering hotbed of rebellion that the Pakistan government has been barely able to contain. Tribal affiliations and alliances throughout Pakistan made the situation untenable. Any direct attack with large forces could possibly set off a civil war that would destabilize the entire region. Any threat to the control of the Pakistan nuclear arsenal or appearance of weakness may have provoked India into mobilizing forces to seal off Kashmir and possibly interfere in the fight. The consequences for the greater region can only be extrapolated from there.
The United States was exactly where it did not want to be: in possession of territory they would have to hold and defend against attacks. Instead of being on the offensive and forcing the Tali-ban and Al Qaeda to react to their moves, they would be on the defensive reacting. Further, bin Laden, though losing the physical battle, had once again won an ideological victory, sealing his mystique as the undefeated, uncaptured and near immortal commander of the "mujihadeen". Their position in Pakistan provided ample opportunity to refit, re-organize, recruit, collect money and materials, and train forces to attack the United States forces in Afghanistan at its leisure as well as plan other terrorist attacks around the world.
The question for the United States was how to mitigate this obvious advantage and force Al Qaeda to fight on the United States' terms?
.After that, comes tactical maneuvering, than which there is nothing more difficult. The difficulty of tactical maneuvering consists in turning the devious into the direct, and misfortune into gain. -Sun Tzu

Was that strategy by accident or design? Most analysts, and several memoirs by members of the military and the administration, seem to indicate that the United States was not prepared to fight a counter-insurgency in Iraq.
The original goals seemed to be two fold: to take out Saddam's regime that could supply money, material, men and training to assist Al Qaeda; and, to establish a democracy in the Middle East that would be able to counter the spread of Islamist ideology through its presence, if not direct interaction, with people in the region. The third unspoken goal was likely to influence leaders in the region that anyone who sought to use terrorists as proxies against the United States would suffer the same fate.
If the United States had planned to draw Al Qaeda and its adherents out of Pakistan and into Iraq for a battle in the heart of the Islamic region, it is very unlikely that any official would acknowledge that in public; neither verbally nor in writing. In setting the stage for battling Al Qaeda and invading Iraq, to separate the region and the people from supporting either out of any sense of ethnic or religious loyalty, the United States had spoken deliberately. In both cases, insisting that the United States was not interested in making war on Islam, Arabs or any greater polity, but had specific, definitive targets and reasons. In doing so, they hoped to mitigate any significant mobilization of nations or the populations as had occurred during the Afghan/Russo War.
Already, the apparent narrative of the war to this date has been written. Not that the United States had planned to draw Al Qaeda to Iraq, but that Al Qaeda took advantage of the mistake in opening a second front. In doing so, providing AL Qaeda an opportunity to recruit more followers, inflict more damage and drain the United States coffers and political will.
If it was not planned, it does seem a tragically fortuitous stumble on to the very strategy that might be the end of Al Qaeda in the greater Middle East. It remains to be seen whether it signals their defeat in Pakistan.
The question remains, why did Al Qaeda believe that they had to go to fight in Iraq?
A combination of things, some having to do with the fact that we *were* smack-dab in the middle of the Islamic World and sitting in the spiritual seat of the Future Caliphate, some having to do with the *huge* over-estimation of Iraqi resentment at us being there, and some having to do with al-Q's view that, as the pre-eminent recruiter for the romance of jihad, it needed to flex it's muscles to show it was still viable.
Then again, maybe they were just worried that the MSM would forget about them...