Complex sentence: On 28 March 1815, during Napoleon I's short-lived return to power (the Hundred Days), Regiments 1-8 of the Guard Tirailleurs were officially re-activated, yet only the 1st and 3rd Regiments actually took the field for the Waterloo campaign.
Split into simpler sentences: On 28 March 1815, during Napoleon I's short-lived return to power (the Hundred Days), Regiments 1-8 of the Guard Tirailleurs were officially re-raised. Only the 1st and 3rd Regiments actually took the field for the Waterloo campaign.