They first appeared as a cloud of dust on the horizon. A few seconds later, the motorcycles carrying Russian soldiers sped into view, zigzagging across a field, kicking up dust, attempting a noisy, dangerous run at a Ukrainian trench.

“They moved fast, they spread out and they swerved,” said Lt. Mykhailo Hubitsky, describing the Russian motorcycle assault he witnessed. It’s a type of attack that has been proliferating along the frontline this spring, adding a wild new element to the already violent, chaotic fighting.

Russian soldiers riding motorcycles, dirt bikes, quadricycles and dune buggies now account for about half of all attacks in some areas of the front, soldiers and commanders say, as Moscow’s forces attempt to use speed…