<P> To encourage pilots to attack enemy balloons, both sides counted downing an enemy balloon as an "air - to - air" kill, with the same value as shooting down an enemy aircraft . Some pilots, known as balloon busters, became particularly distinguished by their prowess at shooting down enemy balloons . The premier balloon busting ace was Willy Coppens: 35 of his 37 victories were enemy balloons . </P> <P> As pioneer aviators invented air - to - air combat, the contending sides developed various methods of tracking aerial casualties and victories . Aviators with five or more aerial victories confirmed by their parent air service were dubbed "aces". Their numbers would burgeon, until by war's end, there were over 1,800 aces . </P> <P> The following aces scored the most victories for their respective air services . </P> <Table> <Tr> <Th> Name </Th> <Th> Air service </Th> <Th> Confirmed victories </Th> </Tr> <Tr> <Td> Baracca, Francesco </Td> <Td> Corpo Aeronautico Militare </Td> <Td> 34 </Td> </Tr> <Tr> <Td> Bishop, William Avery </Td> <Td> Royal Air Force </Td> <Td> 72 </Td> </Tr> <Tr> <Td> Brumowski, Godwin </Td> <Td> Luftfahrtruppen </Td> <Td> 35 </Td> </Tr> <Tr> <Td> Cobby, Arthur Henry </Td> <Td> Australian Flying Corps </Td> <Td> 29 </Td> </Tr> <Tr> <Td> Coppens de Houthulst, Willy Omer </Td> <Td> Belgian Military Aviation </Td> <Td> 37 </Td> </Tr> <Tr> <Td> Fonck, René </Td> <Td> Aéronautique Militaire </Td> <Td> 75 </Td> </Tr> <Tr> <Td> Kazakov, Alexander </Td> <Td> Imperial Russian Air Force </Td> <Td> 20 </Td> </Tr> <Tr> <Td> Richthofen, Manfred von </Td> <Td> Luftstreitkräfte </Td> <Td> 80 </Td> </Tr> <Tr> <Td> Rickenbacker, Edward Vernon </Td> <Td> US Army Air Service </Td> <Td> 26 </Td> </Tr> </Table>

Where did american soldiers fight during most of ww1 apex