From a Wall Street Journal story by Daniel Michaels and Isabel Coles headlined “Ukraine Fights to Widen Its Puncture of Russian Front Lines”:

KYIV, Ukraine—Ukrainian troops’ piercing of Russian lines this week marks a small move with big potential.

The Ukrainians are trying to gradually force their way through the main Russian defensive line in the southeast under heavy fire to expand fissures they opened and achieve a larger-scale breach.

This is a critical moment in Kyiv’s three-month counteroffensive because a full-scale penetration would allow Ukraine to pour armored vehicles through and wreak havoc among Russian forces.