 The Austro @-@ Hungarian assault began at Lazarevac , a strategically located town just south of Belgrade whose capture would have given them access to the <unk> railway line and the ability to outflank the Serbian forces holding the road to Belgrade . Further south , the Austro @-@ Hungarians attacked the Serbian 1st Army . During this assault , they made the mistake of attacking its stronger right flank and were met with determined Serbian resistance which prevented them from gaining any ground . Military historian David Jordan notes that had the Austro @-@ Hungarians attacked the junction splitting the 1st and Užice armies , they might have been able to split the Serbs down the centre and gotten hold of an unimpeded passage to the Morava River . The Serbian 1st Army was quick to reinforce its left flank , realizing that any subsequent attack against it would be far less easy to repel . 
