There Niel led the engineer detachment with one of the storming parties, and his conduct gained for him the rank of chef de bataillon in 1837.

In the first part of the Crimean War, Niel was employed in the expedition to the Baltic Sea and directed engineering operations against Bomarsund.

[1] Niel managed to carry out this delicate and difficult task with as much success as could be expected, and he directed siege operations at the Battle of Malakoff.

In this capacity he drafted and began to carry out a far-reaching scheme of army reform, based on universal service and the automatic creation of large reserves which needed only time to mature.

[1] Niel died in Paris during an operation for a bladder stone, and a year later the Franco-Prussian War destroyed the old imperial army upon which the new formations were to have been grafted.