The Armee de l'Orient had departed from Toulon in May 1798, picking up additional troops from Italy and Corsica along the way. While the ultimate destination had remained a secret until the last possible moment before boarding, preparations had been made for a hot weather campaign with the demi-brigades being reinforced with men recruited from the south of France who would be used to warmer temperatures. After a brief stop in Malta, the expedition reached Alexandria on the 2nd of July.

Even though July is the height of summer, the climate of the Nile delta and Egyptian coast is not remarkably hotter than that of Southern Europe, however it is much drier and temperatures rise quickly once away from the delta. The army had not made any special preparations for the desert climate at the time of landing and the usual European uniforms were worn - for the infantry a woollen blue coat (habit), a white waistcoat (gilet), white breeches, long black gaiters and a bicorne hat (chapeau). The one consideration to the weather seems to have been the Grenadiers putting away their bearskin caps in lieu of a chapeau. Even at the start of the expedition the army's uniforms were already quite worn - there are reports of four regiments wearing decidedly unregulation red and white striped trousers.

After landing, Napoleon began a direct march on Cairo through the desert where the limitations of uniforms designed for campaigning in the Northern European spring became clear. Chef de Bataillon Morand of the 88e demi-brigade complained of the excessive heat causing heavy sweating and a burning thirst. Some troops built portable awnings to serve as sunshades to gain some respite from the heat and many discarded their habits and greatcoats only to suffer during the chilly desert nights. By the time the army reached Cairo on the 25th of July their uniforms were so ragged that Napoleon ordered François Bernoyer, the Chef de l'atelier d'habillement (loosely translated as Chief Tailor) to design and manufacture suitable uniforms.

In a letter dated 28th of July, Bernoyer wrote:

[Bonaparte] asked me to rapidly draw up different uniform designs for the troops, so that he could choose one that would be more convenient for the country and the climate. He advised me to avoid usual constraints on the soldiers’ uniform. From the designs that I presented him the next day, this one was chosen: a very short-cut veste with the lapels buttoned to the waist to replace the waistcoat; cotton trousers finished by half-gaiters, cut so the shoes were well covered to prevent sand penetrating while travelling through desert. … Bonaparte wanted to know how long it would take me to uniform ten thousand men, the most needy of the army. I responded that it would be impossible to give an immediate response, not knowing the country’s resources: He gave me up to 24 hours to inform him. … He appeared satisfied when I told him that I could deliver the ten thousand uniforms in thirty-five days, or two thousand a week, if he gave me the authorisation to requisition all the French and Turkish tailors that I judged necessary. … Three days later my workshop was organised, with more than one thousand craftsmen at work.

One of the rejected designs was for a semi-oriental style uniform. The uniform chosen was made from cotton cloth, dyed blue with indigo. The habit-veste was of a simpler design than the regulation uniform, being only single breasted without the contrasting white lapels; cuffs and collars were red and lining was white. Men were also issued 2 pairs of cotton trousers, short white breeches and a white waistcoat. While this uniform was a dramatic improvement on the European uniform, there were still issues - the gaiter-trousers were ordered to be replaced by half-gaiters and unbleached linen trousers on the 1st of October; the cotton habits were found to be too light to provide adequate warmth at night and grey-white linen or canvas overcoats were ordered on the 21st of September in preparation for the winter. One unexpected change was the replacement of brass buttons with fabric covered wood - the soldiers had discovered that the local Egyptian women enjoyed wearing them as trinkets and were constantly giving them away in an attempt to charm them!

The most visible change was ordered on the 13th of September when the chapeau was to be replaced by leather helmets variously described as casques, casquettes, bonnets de cuir or chackots. These were made from black sheep or goat hides (the order states "bonnets de maroquin" where maroquin is usually taken to mean goat leather, however all references state that they were made from sheep leather). The chapeau had long been noted as providing inadequate protection from the elements, even in Europe, and as a result the new helmets would provide cover for the ears, a large visor to protect the eyes and a foldable flap at the rear to protect the neck. A woolen crest (pouffe) would be have a distinctive colour for each regiment and the French cockade would be carried on the right of the helmet. Grenadiers were to receive red pouffes irrespective of regiment and a flaming grenade badge on the front and rear of the helmet, however it appears that Grenadiers and officers tended to retain the chapeau for as long as possible.