Lets start with the Alte Kommandantur.
The Kommandantenhaus was originally a baroque residential building dating back from 1653, designed by architect Johann Gregor Memhardt. It was enlarged first in 1795-99 to serve as the residence of the Berlin garrison commandant.
The Royal New Guardhouse of Berlin was built by architect Schinkel following the wish of Friedrich Wilhelm III, King of Prussia, for a new guardhouse for the nearby Kronprinzenpalais. The Neue Wache would also serve as a war memorial, since the pediment sculpture was a representation of Nike, the Greek goddess of victory, deciding a battle in the Befreiungskriege (German Wars of Liberation from the French Empire).