What military weapon advancement led to the end of trench warfare?

The hand grenade, long used in crude form, developed rapidly as an aid in attacking trenches. Probably the most important was the introduction of high explosive shells, which dramatically increased the lethality of artillery over the 19th-century equivalents

The hand grenade

Explanation:

the hand grenade, long used in crude form, developed rapidly as an aid in attacking trenches. Probably the most important was the introduction of high explosive shells, which dramatically increased the lethality of artillery over the 19th-century equivalents.

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