I am not sure about the alliance bit but here’s an older encyclical on devotion to the Sacred Heart:
It’s called Haurietis Aquas and was promulgated by Pope Pius XII May 15, 1956.
An encyclical is one of the highest level documents that can be made by Rome, with the Pope being the primary author of the document. The encyclicals usually deal with a faith or morals topic (Magisterial) of a high importance/nature.
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