 Complete the following phrase:  With the rank of Oberst colonel, Rüchel fought against the First French Republic during the War of the First Coalition. During the Siege of Mainz from 10 April to 23 July 1793, he commanded a brigade consisting of the Thadden and Legat Fusilier Battalions and the Wolframsdorf Grenadier Battalion. After promotion to General-major, he led the Prussian contingent during the 