In 1858 Piedmontese and French troops confronted Austrian troops outside of Milan and Menni volunteered to work as a stretcher-bearer to assist soldiers wounded at the battle of Magenta,[1] transporting the wounded from Milan railway station to the nearby hospital.

This brought him into contact with the Hospitallers of Saint John of God; he entered their novitiate in 1860 and took his vows as a member in 1864.

[1] A short time later Menni attracted numerous followers to his cause and this allowed him to establish new institutions of his new order on a rapid scale, not only in Spain but also in Portugal and Mexico.

The 1868 deposition of Queen Isabella II set off renewed persecution and Menni - chosen as the Superior of the order in 1872 - found himself the object of constant threats.

Their work inspired Menni to establish a new women's congregation and accordingly on 31 May 1881 he founded in Madrid the Sisters Hospitaller of the Sacred Heart of Jesus.

Reports of the case also reached Rome and as a result Menni decided to resign as Superior General on 20 June 1912.

Given these health problems, and knowing his end was not far off, he asked to spend the remainder of his life at Dinan in France, where he died on 24 April 1914.

As was the usual manner, after the gathering of documentation and testimonies, the cause was granted formal ratification and allowed to proceed to the subsequent phases, including the compilation of an extensive large dossier to be sent to the Congregation for the Causes of Saints in Rome for further evaluation.

On 11 May 1982, on the advice of the Congregation, Pope John Paul II approved a declaration that Menni had lived a life of heroic virtue and proclaimed him to be Venerable.