To fill a critical shortage of infantry on the front line, Ukraine has embraced one of Russia’s most cynical tactics: releasing convicted — even violent — felons who agree to fight in high-risk assault brigades.

More than 2,750 men have been released from Ukrainian prisons since the parliament adopted a law in May authorizing certain convicts to enlist, including those jailed for dealing drugs, stealing phones and committing armed assaults and murders, among other serious crimes.