Complex sentence: Kitchener was portrayed as a national hero following his drowning in the North Sea on a trip to Russia, which meant that it became part of the good conduct of the war for those involved not to tarnish his reputation.
Split into simpler sentences: Kitchener was portrayed as a national hero following his drowning in the North Sea on a trip to Russia. This meant that it became part of the good conduct of the war for those involved, not to tarnish his reputation.