In 1939 Emmermann joined the U-boat force and in November 1940 became the first Watch officer on UA under the command of Hans Eckermann.

His fifth patrol with U-172 was dramatic, in that the boat brought back half the crew of U-604 which had been so heavily damaged during two air attacks that she had to be scuttled.

Along with some other U-boat men he took part in infantry duty around Hamburg as commander of Marine-Battalion Emmermann.

Emmermann survived the war and later returned to Germany, studied engineering and prospered in business.

[1] As commander of U-172, Emmermann is credited with the sinking of 26 merchant ships totaling 152,080 gross register tons (GRT).