The Delhi Iron Pillar was struck by a cannon ball with the specific aim of breaking the pillar into two. The history of the cannon ball strike has been traced briefly. The trajectory of the cannon ball has been established from the surface features of cannon ball indentation area as well as from the direction of shock wave propagation. The materials science aspects related to the pillar's response to the cannon ball strike have been explained. The nature and origin of cracks surrounding the cannon ball indentation area have been analysed. Visual evidences have been provided to support the sequence of events that followed the cannon ball impact, in a time period of about a microsecond. These included intense plastic deformation leading to creation and propagation of plastic shock wave, initiation of crack at the rear, spallation of material, horizontal propagation of the main crack, and finally branching of the main crack along lump-lump interfaces. The analysis concludes that fracture of the pillar was avoided by deflection of the propagating horizontal crack that originated from the rear end, diametrically opposite the cannon impact area, along the axial direction of the Pillar through lump-lump interfaces.
