Trench warfare has featured prominently during Russia's war in Ukraine. With a summer Russian offensive looming, Ukraine is building and fortifying trenches in the north.

In the Sumy region, which shares a 560-kilometer (348-mile) border with Russia, workers are using earth, wood and concrete to make multiple levels of fortifications. In the neighboring Chernihiv region, which is not far from Ukraine's border with Belarus, the construction of structures known as "Dragon's teeth" and anti-tank ditches is underway.

Ukraine insisted it is not abandoning the aim of recapturing territory from Russia in the east. Right now, defenses like these may be Ukraine's best hope of keeping Russian forces at bay.