The Russian proverb, ‘Trust, but verify’ was made famous by President Ronald Reagan during the height of the US/Soviet arms race. At the time, this was meant to suggest the need for validation, even when there was trust between parties. This phrase was very appropriate as it allowed the two superpowers to become more friendly, but left room for validation that changes were truly being made. Validation begets trust and the situation improved.
Throughout World War I, trench warfare was used by each side to both gain ground and to hold off attacks. These trenches used multiple defenses to slow or stop advancement by troops: parapets, mortar shells, mustard gas, mines, barbed wire and other nasty tools were heavily deployed. This multi-layered approach was implemented to thwart the various attack vectors that the enemy might use. Barbed wire, for example, is effective against soldiers, but not so much against tanks. This is where mines and mortar shells were far more useful. In the famous Battle of the Somme, trench warfare was so difficult that only miles were gained by the end of the war.