By Pavel Polityuk KYIV, Ukraine (Reuters) – Vladimir Putin exhorted Russians to battle in a defiant Victory Day speech on Monday, but was silent about plans for any escalation in Ukraine, despite Western warnings he might use the event in Red Square to order a national mobilisation. In Ukraine, there was no let-up in fighting, with Kyiv describing a stepped-up Russian offensive in the east and a renewed push by Moscow to defeat the last Ukrainian troops holding out in a steelworks in ruined Mariupol. Monday’s annual Victory Day celebration in Moscow – with the usual parade of ballistic missile…