Complex sentence: At the outbreak of the French Revolution Swiss regiments, as foreigners considered more reliable than their French counterparts in a time of civil unrest, made up a significant proportion of the royal troops summoned to Paris by Louis XVI in early July of 1789.
Split into simpler sentences: At the outbreak of the French Revolution the Swiss troops were, as foreigners, considered more reliable than their French counterparts in a time of civil unrest. Accordingly Swiss regiments made up a significant proportion of the royal troops summoned to Paris by Louis XVI in early July of 1789.