Final answer:
The cleverness of World War I soldiers was necessitated by the deadly new technologies of trench warfare, which made traditional acts of heroism obsolete. The massive casualties and psychological impact of the war led nations to question the very meaning of victory, with the Treaty of Versailles further complicating post-war sentiment.
Step-by-step explanation:
World War I soldiers needed to be clever to survive the harsh conditions of trench warfare and the new, deadly technologies of war. The tactical problem during this period was that offensive strategies which had been effective in previous conflicts were now obsolete due to the defensive advantages provided by trenches, machine guns, and other modern weaponry. This led to a brutal stalemate where neither side could gain significant territory without enormous casualties, exemplified by the phrase 'going over the top', which resulted in high death tolls for attacking soldiers.
In addition, the psychological impact of the war and the post-war period saw nations grappling with the consequences of such a devastating conflict. Soldiers saw heroism as irrelevant in the face of mechanized warfare, while nations reassessed what 'winning' meant, with many citizens falling into despondency and conspiracy theories. Moreover, the Treaty of Versailles inflamed German resentment by forcing them to accept sole responsibility for the war, setting the stage for further conflict.