A battle now rages, in the course of which various knights perform great deeds, but, although Godfrey proves victor on this occasion, he loses Dudon, chief of his Adventurous Band and one of the bravest warriors in his army.  While giving her explanations to Aladine in regard to the fight waged beneath their eyes, Erminia carefully explains she feels deadly hatred for Tancred, although the truth is she loves him dearly and is greatly relieved to see him escape from the fray uninjured.

Many people having died in the course of this action, a truce is agreed upon so that both sides may bury their dead, and so, many funerals are celebrated with all due pomp and ceremony.  Next the crusading force decides that siege-engines and towers will be necessary to enable them to scale the high walls of Jerusalem.  They therefore send out a force of woodsmen to hew the trees which are to serve for the construction of the required towers.

    The duke, when thus his piety had paid
    The fun’ral rites, and shed his duteous tears,
    Sent all his skill’d mechanics to invade
    The forest, guarded by a thousand spears;
    Veil’d by low hills it stood, the growth of years,—­
    A Syrian shepherd pointed out the vale,
    And thither brought the camp-artificers
    To fabricate the engines doom’d to scale
  The City’s sacred towers and turn her people pale.

Canto IV. The scene now changes to the infernal regions, where Satan deems it time to frustrate the Christians’ aims, because it would ill-suit diabolical ends to have them recover possession of Jerusalem.  Not only does Satan stimulate his hosts by reminding them of their forfeited bliss, but he encourages them to thwart the Christians by reminding them of the great deeds they have already done.  His eloquence is not expended in vain, for the fiends all approve of his suggestions, and, when the council is over, flit forth, intent upon fomenting dissension among the leaders of the Crusade, and hindering their attempts in every other way possible.

One demon in particular is to determine a wizard to send his niece Armida to ensnare the Christians.  This enchantress, decked out with all the charms beauty and toilet can bestow, soon appears in the Christian camp, where, falling at Godfrey’s feet, she proceeds to relate a tale of fictitious wrongs, claiming to be heiress of the city of Damascus, whence she has been ejected, and vowing if she could only secure the aid of a few knights she would soon recover her realm.  In return for such aid as she implores from the Christians, she promises to do homage to them for her realm, and even pledges herself to receive baptism.  Her artful speeches, the flattery which she lavishes upon Godfrey, and her languishing glances are all calculated to persuade him to grant her request; but the Crusader is so bent upon the capture of Jerusalem that nothing can turn him aside from his purpose.