I'm not so convinced. Alliances at the strategic level were common, however, I am less sure that these resulted in actual battlefield cooperation - so you might get 2 states invading a third, but their armies would act independently.
Qin may be different in that they incorporated defeated enemies into their army - but may that just be slightly different troops to native Qin ones?
That said, my real interest with China starts with the Han so I may well be barking up the wrong tree here.