In 'Nam the typical tactic employed by MiG pilots was to stay low while being directed on to the target intercept, where they'd be hard to see visually below cloud cover and lost in the terrain to both radar and sight, and then "pop up" to ambush the target... GCI ( Ground Control Intercept) Controllers guided the flight on to the correct target path and to the interception until the MiG's were in range to acquire the enemy aircraft with their limited on-board radar sets. At that point the MiG Pilots would climb out of the ground clutter, engage with missiles and guns, then power into a dive using the ground clutter again for a low altitude escape... This sort of "hit-and-run" tactic was highly successful and Vietnamese Pilots racked up impressive kill scores through the course of the war... MiG-21 PFM Fishbed and extras by me Rendered in DS 2.3