Dr Farhan Zahid (Pakistan), Ph D, is a Counter-Terrorism and Security Analyst.
Lashkar-e-Taiba (LeT) is considered to be most lethal, highly organized and disciplined Islamist violent non-state actor in Pakistan. According to prominent expert on Pakistani terrorist organizations, Professor Christine Fair's, Al-Qaeda in Pakistan is more in need of LeT than LeT in need of developing an association with Al-Qaeda. It is mainly because of strong LeT roots in Pakistan, its connections with a plethora of jihadi organizations in both Pakistan and abroad, and jihadi infrastructure and its presence in terms of organizational size and number.
LeT has its roots in Afghan War. It was a late entrant into the conflict (duringthe last days), inevitably had no significant role to play. LeT was established by Abdullah Yousaf Azzam who is also considered as co-founder of Al-Qaeda and its principal ideologue. Earlier, he laid the foundations of Saudi funded Maktab-ul-Khidmat wal Muhajireen, or services office, in Peshawa,r in 1981 which was later rechristened into Al-Qaeda by Arab veterans of Afghan War, led by Bin Laden, in 1988.
Two former members of Islamist political party Jamaat-e-Islami (JI) - also professors of Islamic Studies at University of Engineering and Technology, Lahore - Professor Zafar Iqbal and Professor Hafiz Saeed, presented the idea to Abdullah Azzam of creating a separate militant Islamist organization purely on Wahabi/Salafist lines, rather than working alongside Deobandi Islamist groups such as Harkat ul Jihad Islami (HuJI) and Harkat ul Mujahedeen (HuM). Azzam was the focal person for getting Saudi-Kuwaiti funding for Afghan War (along with his protégé Bin Laden). Azzam and Laden provided the seed money for the creation of LeT and it surfaced in 1988 in Kunar province of Afghanistan.
Amongst mujahedeen groups, there had been at various occasions, severe rifts because of the interpretation of religion. Most of Peshawar Seven groups were followers of radical Deoabndi (a derivative of Saudi-Wahabi sect which is even harsher) sect of Islam, whereas Arab mujaheeden (calling themselves Arab-Afghans) were all strict followers of Wahabi/Salafist doctrines. These serious problems led to struggles for power and, due to their low strengths amongst Afghan jihadi groups, the Wahabi Arabs (aka Arab Afghans) wanted to form their own organization. The very reason paved the way for the formation of LeT which was created in the Wahabi strongholds of Afghan Kunar and Nuristan provinces.
It is quintessential to note here that LeT is the militant wing of a proselytizing/missionary organization. Hafiz Saeed, Azzam, Zakki ur Rehman Lakhvi and Zafar Iqbal created Jamaat-ud-Dawa (Party for preaching) and then its political wing Markaz-al-Dawa.wal-Irshad (Center for preaching and guidance) ; and it was from this platform they established its militant arm, LeT. 
Figure 1: JuD Structure
The LeT and its founding members wanted to play a bigger role in Afghan War, but indeed they were latecomers. The Afghan War was about to end as Soviets had already signed the Geneva Accords in 1988 and last of their troops withdrew from Afghanistan in early 1989. The LeT was truly the tool what Saudis and other Arab Wahabi states had always envisioned to use in Afghanistan for showing their resolve for defeating the Soviets. It was created with the Saudi money and its ideology and proselytizing activities, alongside with politics and charity work, was all set to promote Wahabi/Salafist version of Saudi Islam in Afghanistan and Pakistan (two predominantly Sufi and Shia sect countries).
Previously, the Saudi money had gone mostly into the hands of Islamist groups which were adhering to Islamist radical thoughts similar to theirs, but that were not exactly what Saudis had wanted to achieve. The Saudis were in competition with the Iranians who had been able to cultivate allies within Shia Mujahedeen groups. It was only Abdul Rab Rasul Sayal's party, Ittehad-e-Milli (Islamic Unity), that was clearly on terms with Saudi government. But Sayal and his party were too weak to achieve any of the desired objectives and had failed miserably. Saudi long term objectives in Afghanistan's war-theatre were dashed but LeT's framework and funding were utilized by Pakistani Islamists in Indian Kashmir Islamist insurgency. 
The LeT attack on Indian parliament was an ample proof of its support to Taliban and Al-Qaeda that had been under siege during Pakistan army operations against the runaway elements of these two entities. The amassing of Indian troops at Pakistan's eastern borders had pushed Pakistan to shift its forces from western to eastern borders. Those forces were engaging Al-Qaeda and Taliban remnants and therefore their westward shifting gave Islamist militants breathing space.
Arrest of LeT activist Ajmal Kasab during Mumbai attacks brought LeT into world focus. More than 183 citizens belonging to 27 countries lost their lives in Mumbai attacks in 2008. Pakistani authorities blamed non-state actors for executing those attacks and offered cooperation for investigations. Arrest of another LeT activist involved in Mumbai attacks was Dawood Gillani (aka David Headly), arrested in the US. Gillani was charged for providing logistical assistance to LeT planners Zaki ur Rehman Lakhvi and others for Mumbai attacks. 
LeT was amongst the organizations banned by General Musharraf in January 2002, after December 13 2001 attack on Indian Parliament in New Delhi. The terrorist operation was indeed a joint-venture of LeT and Jaish-e-Mohammad, another Kashmiri Islamist terrorist group active in Indian Kashmir insurgency. Since then, LeT has changed the course of activities and Hafiz Saeed and Lakhvi were briefly arrested while many others have gone underground. JuD and LeT headquarters near Lahore were raided by law enforcement agencies and sealed off for a period of time.
Apart from these two major brazen acts of terrorism, LeT, since its launch in Kashmir insurgency, was instrumental in hundreds of acts of violence. Amir Rana describes the magnitude of LeT activities as "according to Lashkar-e-Taiba records, of its ten thousand trained mujahedeen, six thousand are active in jehadi activities in occupied Kashmir. Doctor Manzoor Ahmed, an important member of Jamaat-ud-Dawa, has prepared a record of eleven years of Lashkar-e-Taiba's militant activities. According to this record LeT killed 14,369 Indian Army personnel and officers during this period and lost 1 016 of its own men." 
Stephen Tankel, a leading expert on LeT, explains LeT's ideology as pan-Islamist and global. A glaring proof is LeT's involvement in wars in Bosnia, Tajikistan and Afghanistan. He further elaborates that unlike other jihadi groups, LeT does not recruit from madrasahs but from branches of its own schools and also from government schools. The focus is always on first converting the recruits to Ahl-e-Hadith (Wahabi) ideology before going any further. 
According to Tankel, LeT had field days during Kashmir insurgency and it never restricted itself to Indian Kashmir region and kept on attacking targets in mainland India, such as Red Fort attack 2000, Indian parliament attack 2001, and Mumbai attacks 2008. The heydays of Kashmir insurgency seemed to end after 9/11 attacks and Pakistani military regime took a U-turn, showing they were not keen to back Insurgency in Kashmir. Despite of GWOT, some level of Islamist militancy continued in Kashmir and LeT remained active for a while.
One major terrorist incident involving LeT was Mumbai attacks in 2008. In the aftermath of Mumbai attacks, Pakistan faced immense pressure to dismantle the LeT infrastructure. But despite of that, military regime of General Musharraf reacted only superficially. Moreover, the LeT, unlike other Pakistani Islamist violent non-state actors, has not yet stood up against the state of Pakistan and challenged the write of state in the post-9/11 scenario, whereas most of the former Pakistan-backed groups have turned to violence in support of Al-Qaeda and Afghan Taliban. Therefore, it seems likely that, LeT would turn to other fronts, "barring a decision to turn on the Pakistani state this leaves LeT with four areas on which to focus: fighting in Afghanistan; launching terrorist attacks against India; participating in the global jihad via terrorism against the US and its allies; and non-violent activism in Pakistan, primarily through the provision of social services." 
The question is how long Islamist hardliners in Pakistani military establishment, and especially in intelligence agencies, would not take on LeT. Islamist violent non-state actors like LeT are unpredictable and could not hold on to restricting to operations where only their handlers want them to operate.
Consistent pressures on Pakistan are increasing from international community, especially from the US and allied forces in Afghanistan. Presence of LeT elements in operations against the US forces side by side Haqqani Network in Afghanistan is now visible. Some of LeT's splinter groups (Al-Arifeen and Al-Qanun) have joined hands with other Islamists mujahedeen groups. Some high value Al-Qaeda targets have also been arrested from LeT safe houses in Pakistan. One good example is of Abu Zubaidah, arrested by Pakistani security forces in Faisalabad, Punjab province, from a LeT office, in 2003.
On May 2, 2011, the LeT leaders under the garb of JuD protested against Bin Laden's killing in Abbotabad operation (operation Neptune Spear) conducted on May 1, 2011. It was only the LeT leadership and members in Pakistan who led processions in condemnation of the attack on the streets of Karachi and Lahore.  In Lahore the LeT mourned the death of Bin Laden.
LeT's growing association with Al-Qaeda is not unnatural and it is only a matter of time when LeT would unleash itself against the state. The rebellion against the state would be either because of international pressure or factionalization within the LeT ranks. Since the organization revolves around the personality of Hafiz Saeed, therefore the possibility of fragmentation is likely in case of any internal rifts.
The LeT's merger into Al-Qaeda Central is inevitable as it is very much likely because of adherence to similar Salafist/Wahabist beliefs. Currently, the LeT is armed to the teeth and its tentacles are spread all over Pakistan. Its transformation into a full-fledged anti-state Islamist violent non-state actor is something inevitable and its ideological affinities with Al-Qaeda, as well as its politico-religious ambitions, are diametrically opposite to the Pakistani constitution and the state's working apparatus.