And clearly he means military action, not interior spiritual struggle. All the schools of Islamic jurisprudence agree that when a non-Muslim force enters a Muslim land, jihad becomes the individual obligation of every Muslim (fard ‘ayn) rather than a collective obligation of the entire umma, from which one is released if others are taking it up (fard kifaya). Bulghah al-Salik li-Aqrab al-Masalik fi madhhab al-Imam Malik (“The Sufficiency of the Traveller on the Best Path in the School of Imam Malik,”) says this:

Jihad in the Path of Allah, to raise the word of Allah, is fard kifayah [obligatory on the community] once a year, so that if some perform it, the obligation falls from the rest. It becomes fard `ayn [obligatory on every Muslim individually], like salah and fasting, if the legitimate Muslim Imam declares it so, or if there is an attack by the enemy on an area of people.

The Hanafi, Maliki, and Shafi’i schools of Sunni jurisprudence further declare that jihad, once it is fard ‘ayn, is no different from prayer and fasting — in other words, to engage in warfare with non-Muslims in that case is a religious devotion that cannot lawfully be evaded. Hashiyah Ibn `Abidin, an authoritative text of the Hanafi school, says that jihad is “fard ‘ayn if the enemy has attacked part of the Islamic homeland. It thus becomes an obligation like salah [prayer] and fasting which cannot be abandoned.”

“Egyptian Islamic Scholar Ibrahim Al-Khouli: We Must Conduct Jihad against the West, Who Are Aggressors against the Land of Islam,” from MEMRI, September 25:

Following are excerpts from an interview with Egyptian Islamic scholar Ibrahim Al-Khouli, which aired on Azhari TV on September 25, 2010: […]What formula should the Islamic nation adopt in its dealings with America and the West? […]

Ibrahim Al-Khouli: We must confront them, and say: You are aggressors on the land of Islam. You are occupying our lands. You are exploiting our resources. You are humiliating our people. Unless you stop doing that, and restore our rights, the only path we will take is the path of Jihad, which is an individual duty incumbent upon the nation.

Interviewer: Yes.

Ibrahim Al-Khouli: Forget about Bin Laden and Al-Qaeda. That’s not what I’m talking about. I am talking about the Jihad of the entire nation.

Interviewer: Not of individuals.

Ibrahim Al-Khouli: I’m talking about Jihad which is led by the Islamic scholars, and the entire nation will be mobilized for the sake of the supreme Jihad. This will lead us to a confrontation.

[…]

We should follow the example of the young men of the Taliban. A group of several thousands of students have been crushing NATO in Afghanistan and Pakistan. Where are the armies of the Muslims?