The first shipment of Leopard 2 tanks from Germany has been sent to Ukraine.
German defence ministry says 18 cutting-edge main battle tanks were delivered after Ukrainian crews were trained to use them.
Defence Minister Boris Pistorius said he was sure the tanks could make a decisive contribution on the frontlines of Ukraine's war with Russia.
According to reports from Ukraine, Challenger 2 tanks from the UK have also arrived.
Ukraine has been calling for more modern vehicles and weapon systems for months to help fight Russia's invasion.
Around 2,000 Leopard 2s, widely regarded as being among the best main battle tanks produced by Nato countries, are in use by European countries.
Germany agreed to supply the tanks to Ukraine in January, after being initially reluctant to do so - or even to permit other countries from sending their own.
Under German law, Berlin must approve Leopard 2s being re-exported by any country.