Migrating Federal Monsters

Strategies and Tips for migrating monstrous websites from mixed sources (Drupal, static html, Cold Fusion, custom CMS ... ) into Drupal.  Based on the experience of moving several large federal websites composed of multiple combinations of legacy sites and sub-sites into one cohesive Drupal site. Federate multiple sites into one without broken links or loss of SEO history.  The concepts are version agnostic and apply for both Drupal 7 and Drupal 8.