BERLIN, March 27 (Reuters) - The 18 Leopard 2 battle tanks pledged by Germany to support Ukraine in its war against Russia have arrived in Ukraine, the German Defence Ministry said on Monday. Germany agreed in January to supply the tanks, regarded as among the best in the West's arsenal, overcoming misgivings about sending heavy weaponry that Kyiv says is crucial to defeat Russia's invasion but Moscow casts as a dangerous provocation. See here for a complete list of exchanges and delays