According to Sheikh Abdullah Azzam who was the Ustadh of Usama Bin Ladin, Jihaad is Fardh-e-Ain.

Answer

Jihaad is an integral Institution of Islam. Denial of Jihad as the modernists do, is kufr. Those whose brains have been colonized by the U.S.A. and the West in general, deny Jihaad to appease their colonial masters who have securely embedded their brains in their colons. However, in the present age and circumstances, Jihad is not Fardh-e-Ain. Fardh-e-Ain means Fardh on every member of the Ummah – male and female, in the same way as the daily Salaat is Fardh-e-Ain. The claim that Jihaad is Fardh-Ain, i.e. compulsory on every member of the 3 billion strong Ummah is ludicrous. This preposterous averment portrays the superficiality of the knowledge of the claimant.

Sheikh Abdullah Azzam was a Salafi. According to Salafis, their Jihaad activity is fardh-e-ain. This view is palpably baseless.