Rudolf Eickemeyer

Jean Marie Rodolphe Eickemeyer (11 March 1753 - 9 September 1825), also called Heinrich Maria Johann Rudolf Eickemeyer, was an engineer, mathematician, and general of the French Revolutionary Wars. Eickemeyer was born on in Mainz, and died in Gau-Algesheim, a town in the Mainz-Bingen district of present-day Rhineland-Palatinate.

Originally in the service of the Elector of Mainz, after the fall of Mainz in 1792, he served in the French Republican Army, attaining the rank of general of brigade, and commanded a division at the Siege of Kehl (1796–97). He left French service in 1799 and retired to Mainz, but found no employment there. He moved to his hometown, where he served two terms as mayor, and was elected as a deputy to the Chamber of the Grand Duchy of Hesse.

Eickemeyer's father came from Eichsfeld, and had studied mathematics in Göttingen and then at the ducal college in Mainz, and led him through his earliest studies, giving him a solid grounding in the sciences. In 1770, he entered the school of Artillery in the position of an officer. Before taking a position of professor of mathematics at the university, he went at the end of January 1775 to Paris, to study for a half year, and then visited the Netherlands and England. In particular, he study the workings of water and its relationship to military architecture. After his return to Mainz, he began to lecture, but was also in the military service and civil administration, gradually acquiring more responsibility and authority as he became a lieutenant colonel and director of hydraulics.

By 1779, he was the chief engineering officer and had responsibility for the reinforcement and expansion of the Mainz fortifications, which were sadly depleted. However, the Elector of Mainz were adamantly against the investment in the strengthening of the Mainz fortifications, and not until after the outbreak of the French Revolution was there any interest in military affairs. The 1790 campaign against the insurgents of Liege was made; Eickemeyer also commanded the Elector's army, but by then it required so little of his time that he was able to resolve an engineering problem for the Munich Academy.

As early as 1791 the other monarchies of Europe watched with alarm the developments in France, and considered whether they should intervene, either in support of Louis XVI or to take advantage of the chaos in France. The key figure, the Holy Roman Emperor Leopold II, brother to the French Queen Marie Antoinette, had initially looked on the Revolution calmly. He became more and more disturbed as the Revolution became more radical, although he still hoped to avoid war. On 27 August 1791, Leopold and King Frederick William II of Prussia, in consultation with emigrant French nobles, issued the Declaration of Pillnitz, which declared the interest of the monarchs of Europe in the well-being of Louis and his family, and threatened vague but severe consequences if anything should befall them. Although Leopold saw the Pillnitz Declaration as a way of taking action that would enable him to avoid actually doing anything about France, at least for the moment, Paris saw the Declaration as a serious threat, and the revolutionary leaders denounced it.

The Elector of Mainz seemed unfazed by the military violence in France, but he eventually realized that the problems in France would spill into the Rhineland, especially when the Louis XVI's brothers and cousins were agitating for their restoration and using Mainz as a basis for counter-revolutionary action. Eickemeyer was charged with developing a plan for Mainz's defenses. Based on his proposal, the gates were reinstalled and the trenches repaired. In addition, palisades in the outer works improved Mainz's defensive capabilities. Work proceeded slowly, despite the launching of the campaign by the Holy Roman Emperor and the King of Prussia against the French Republic. When news arrived of the capture of Speyer by Custine, work elevated to a frenzy, as local leadership tried to catch up with great zeal on what they had not done in the previous ten weeks, and even ten years. Regardless of the pending panic, though, the Archbishop insisted that his own timbers be purchased to reinforce the walls, further lining his own pockets.

As the French approached, the important defensive points were occupied and ready. In Mainz, though, there was panic: the regiments of the Duke of Nassau evacuated the fortress on October 5. The Elector, the gentry, the bishops, the aristocrats and their servants quickly left the city. It is estimated that between a quarter and a third of the 25,000 inhabitants fled. The rest of the population declared themselves ready to defend the decrepit fortifications. They had 5,000 volunteers, which was clearly insufficient to cover the city's huge physical plant.

Eickemeyer could see that although there were approximately 20,000 troops, they only had field artillery, not siege equipment, and a city the size of Mainz, even as poorly fortified as it was, would require specialty equipment. Custine sent word for a capitulation and the city fathers had a meeting on their situation. The French troops, now called Army of the Vosges by decision of the Convention, began the encirclement and siege of the city on October 18. On that night, the vanguard of General Jean Nicolas Houchard reached Weisenau.