Determining the behavior of functional materials under irradiation is important for fundamental understanding of order-disorder phenomena as well as control of performance in extreme conditions for applications such as nuclear reactors or spacecraft. Prior studies of model oxide interfaces have found that certain interface configurations may be more robust to amorphization under irradiation [1]. These findings raise the question of how initial defect distributions with a thin film may affect the evolution of disorder and how such populations can be tuned to guide the radiation response. Here we study the progression of disorder in oxide thin films using analytical scanning transmission electron microscopy, revealing how intrinsic defect populations guide disordering pathways. To determine how different initial states affect the accumulation of disorder due to ion irradiation, we have examined the material system La 1-x Sr x FeO 3 (LSFO) grown on SrTiO 3 (001). Thin films are epitaxially grown by pulsed laser deposition and molecular beam epitaxy, producing largely single crystal films, with some additional LFO films grown containing columnar defect domains. To investigate the different stages of disorder leading to amorphization, films were masked and irradiated to progressively higher doses in quadrants