Complex sentence: The XA-22 was not adopted for operational service in the US, as the contract was won by Douglas with its A- 20, but Martin received foreign orders, and about 450 of these relatively fast, twin-engined planes were built.
Split into simpler sentences: The XA-22 was not adopted for operational service in the US as the contract was won by Douglas with its A- 20. But Martin received foreign orders, and eventually about 450 of these relatively fast, twin engined planes were built.