Merz, right, with his Vice Chancellor and Finance Minister Lars Klingbeil, who has warned of 'too many arguments in this government'

German Chancellor Friedrich Merz has driven sweeping changes in security, economic and migration policy during his first 100 days in office, but faces widening cracks in his uneasy coalition.

On election night in February, a jubilant Merz promised to bring a bit of "rambo zambo" to the post -- using a colloquialism that can evoke a wild and joyous ride, or chaos and mayhem.