Integrated modeling is a valuable tool for analyzing complex optical-mechanical systems such as the James Webb Space Telescope. An implementation, the Integrated Telescope Model (ITM), has been developed for JWST to analyze the performance of the Observatory. ITM is an end-to-end physical math model starting from stellar photons through the image produced by the science data pipeline. The model also includes all effects that contribute to the formation of the image including pointing errors, vibration and thermal distortions of the optical system, and the mechanical response of the mirrors and actuation devices. A time domain interface to the attitude control system rounds out the capabilities. The model is used over the life-cycle of the JWST program including: development, verification and on-orbit operation. ITM is used to perform verification analysis on the set of test data resulting in a statistical assessment of the expected observatory performance. This capability offers numerous advantages to the verification of the system, validation of the wavefront sensing and control (WFS&C) system along with system level studies for design assessments. ITM has been developed to interface to the ground control system in the same way as the actual observatory. This allows it to be used as substitute for the Observatory for training, mission planning and operational trades.