I would just like to make a correction with regard to the 'invention' or 'development' of the tank and the submarine.
Tank - invented 1914 by Ernest Swinton - idea was borne in 1900 during the Boer war, as a defence against automatic machine guns and barbed wire. Was not 'invented' or 'deisgned' per se until Swinton recieved a letter from the British home office, when he set about trying to fit an automatic machine gun on a Holt tractor.
Submarine - first built in 1624 by a man named Drebbel - was not effective or efficient, and certainly not used as a machine of war at this time, although the 'invention' of the submarne is credited to 'William Bourne'.
By 1914 both the British and Germans had submarine fleets which were put to military use. Many submarines of WW2 were still of 1914 designs, but improvements were made, but probably the biggest step forward was that of the tactical use of submarines 'the wolf pack' as it was termed in germany, and shortly later, 'hunter killer' as an allied tactic. There is a lot of history on developments of the submarine available between the 'invention' and the 20th century. The Royal submarine museum in Portsmouth, UK , have their own website which i am sure you will find interesting.