In the wake of the terror attacks that killed more than 180 people (including at least six Americans) and wounded another 300 in Mumbai, India, last week, the burning question is: Who done it - and why?

It's still speculative, but most fingers are pointing toward Pakistan and such terrorist groups as Lashkar e Tayyiba (LeT) and Jaish e Mohammed (JeM).

Yes, the attacks could've been homegrown. India is home to more than 150 million Muslims, including several active Islamist terror groups - one of which claimed responsibility for the attack early on. But few believe these indigenous groups could've pulled off such a well-coordinated, sustained assault without outside assistance from a highly capable foreign organization.

Some have mentioned al Qaeda because of the attack's relative sophistication - and the simultaneity of the numerous strikes across Mumbai, India's financial and (Bollywood) entertainment center.

The Indians claim al Qaeda doesn't exist in their country, and the lack of suicide bombers lends credence to the idea it wasn't Osama's cronies. Yet his direction or inspiration for an attack can't be ruled out - many of the suspect groups have al Qaeda ties.

Which leads us back to the notion the attacks were orchestrated by the likes of LeT and JeM.

In fact, the early investigation in Mumbai is focusing on a ship that may have carried the attackers from Pakistan to the waterfront near the Taj Mahal Hotel, one of their targets.

If it's a pack of Pakistanis, their likeliest motive was the disputed territory of Kashmir, which India has held but Pakistan has also laid claim to since the two nations divided on gaining independence from Britain in 1947.

Kashmir has driven Islamabad and New Delhi to become enemies, leading to three wars and propelling both to become nuclear-weapons states in 1998.

Regaining Kashmir is the goal of LeT and JeM, which have attacked India repeatedly - including a strike against the federal parliament, which nearly brought India and Pakistan to blows again in 2002. Both groups were established by Pakistani intelligence - the roguish ISI - to destabilize India and create pressure for concessions on Kashmir. (Islamabad has denied any government involvement this time.)

Indeed, the motivation for these strikes could be putting the kibosh on improving Indo-Pakistani relations under new Pakistani President Asif Ali Zardari (the widower of the slain pol Benazir Bhutto).

He has been making peace overtures to Indian Prime Minister Manmohan Singh, hoping to improve economic and trade ties between the two South Asian giants to help Pakistan's struggling economy. This led LeT's founder to say Zardari was growing too "dovish" on India. Zardari may have also added fuel to the fire by referring to Kashmiri resistance groups as "terrorists" rather than freedom fighters.

Thus, the terrorists may have felt the need to halt any improvement in New Delhi-Islamabad ties, especially if it prevents Pakistan from giving up the Kashmir struggle. They'd likely find some terror groups, such as Indian Mujahedeen, willing to assist with such an effort.

Another attack on India with even a whiff of Pakistani government involvement would kill any chance of better relations - and maintain the terrorists' leverage over Pakistani policies.

If there's any glint of hopeful news, it's that Islamabad may finally take tougher steps to rein in JeM and LeT. (We've already seen some improved efforts recently against the Taliban and al Qaeda in the tribal areas near Afghanistan.)

Zardari's offer of full cooperation with India may help restabilize relations between the neighbors. The early challenge is a possible Indian military response against Pakistani interests, which could lead to escalation.

The tragedy also provides Washington an opportunity for greater counterterror cooperation with both Islamabad and New Delhi - an idea both may be open to now. That step would make us all safer.

Peter Brookes, Senior Fellow at the Heritage Foundation, is a former deputy assistant secretary of Defense.