 As a result of the heightened tensions, on 23 April the 421 Tactical Fighter Squadron was established at Kunsan and attached to the 354 TFW.F-4Es from Eglin AFB were deployed to Kunsan and assigned to the 421st, with support personnel from the 4th TFS – deployed from Eglin to Da Nang Air Base South Vietnam were sent TDY to Kunsan to support the 421st.At the end of tensions on 26 June 1969, the 421 TFS was inactivated at Kunsan, with the aircraft being sent to Da Nang as replacements along with the TDY personnel.