The main reason germany issued the sussex
pledge in 1916 was to

The main reason Germany issued the Sussex  Pledge in 1916 was to maintain diplomatic relations with the United States.

Explanation:

On March 24, 1916, the Germans accidentally attacked a French passenger vessel called 'the Sussex' in the English Channel. Fifty people died, while Several Americans got injured. Woodrow Wilson, the US President, insisted that Germany must stop sinking passenger vessels. Otherwise, America will 'break off' diplomatic relations with Germany.

As a response, Germany issued the Sussex Pledge, which states that adequate warning will be given before attacking any passenger ships, while the safety of the passengers will be ensured.

missouri compromise of 1820 which prohibited slavery