Was the convoy system successful? why or why not?

The convoy system is the system of employing naval protection for merchants or troops. That means that the enemy who  would want to damage the other side by cutting off their supplies would have to face more resistance.
This system was especially successful in the First World War, and it was said to contribute greatly to winning, as it was the German strategy to cut their enemies off from possible suplies (such as from the US).