"German Government since the outbreak of hostilities in August 1914. "
A lie - Germany supplied weapons to the Republicans because they believed it would be a hindrance to Britain's war effort - the supplying of weapons was the only contact they had with the rebels and it had nothing whatever to do with the executions and was never claimed to be the reason - you have made that up - as you do.
Britain executed the rebel leaders as an example of what would happen if the Irish stepped out of line again, nothing more.   
As you don't link your claims, you have no evidence for your inventions.
Had wartime treason been the reason, everybody who participated in the rebellion would have been executed.
Incidentally, The Black and Tans served in Ireland from the end of 1919 to some time in 1921 (exact date hard to establish but many of the Tans joined the RIC and remained there up to 1922 - they were responsible for many of the atrocities committed by that took place during the War of Independence.