The rivalry with Istrice:
Before their recent heated rivalry was born, Lupa and Istrice were even allies. They were trivial border issues, born in the thirties for a dispute of a few meters, which gave rise to the first disagreements. The reason for the dispute was who could put their flag on the corner of via degli Umiliati. In order to restore serene relations, a commission was set up, but was unable to get the parties to agree. The tension rose to the two Palii of 1935, when in July the Lupa won and in August Istrice, in both cases with the great Ruello. The Unique Numbers published on those occasions by the two Contrade reported serious reciprocal claims and the classic Paliesque teasing that characterize every Sienese rivalry: a rivalry that has never subsided since then.
From: Wikipedia, l'enciclopedia libera.