The Battle of Loulin was fought in Winter 645 BC between the states of Chu and Xu, the latter being supported by a coalition of northern states led by Qi. Xu, originally the most powerful state of the Huai River valley, had been weakened by internal unrest and several wars since the beginning of the Spring and Autumn period. As its influence over eastern Hubei, southern Henan and central Anhui waned, Chu began to expand into these regions. Threatened by these developments, Xu joined an alliance of several northern states against Chu. In spring 645 BC, when Chu invaded Xu's southern heartland, the northern states sent a relief expedition in order to aid Xu and stop Chu's eastern conquests. The coalition forces eventually met Chu's army at Loulin and were defeated, marking the beginning of X