As a fighter, the P-51 Mustang was a classic; as a ground support weapon, not so much. The under fuselage oil cooler was its most vulnerable point — one hit there and the engine would seize solid in 10 minutes when it ran out of oil. The radial engined P-47 Thunderbolt was the toughest fighter-bomber when it came to ground support. Well armed and armored, the P-47s air-cooled radial engine kept running when it took battle damage and brought its pilot home. A Mustang pilot would have had to walk home through occupied territory. The Thunderbolt's eight .50 calibers, two 500 lb. bombs and ten 5-inch rockets could really ruin an enemy's day.
Today's A-10 is the USAF equivalent to the WW2 P-47. The official name for the A-10 is Thunderbolt II. The F-16 Fighting Falcon is equivalent to the P-51 Mustang — and just as vulnerable doing the job of close air support (CAS). If the USAF is successful at retiring the A-10, the US Army or other ground forces will loose their best and most effective CAS weapon. And, NO, the F-15E or F-35A or F-16C...none can assume the role of the A-10 and survive.