Ukraine Says It Shot Down Kinzhal Missiles, One of Russia’s Most Advanced Weapons

“We wouldn’t be committing this amount of weapons to Ukraine at this point, if the thinking was that it was not likely that they would succeed,” said Mr. Kirkegaard, who is now a senior fellow at the German Marshall Fund research group in Brussels.

Some Western officials hope that if the Ukrainians make substantial gains of territory, they would have more leverage in any peace negotiations.

Just last week, Mr. Zelensky had warned that the anticipated counteroffensive against Russia that was expected to begin this spring or early summer could be delayed unless Kyiv quickly received more weapons.

European allies responded in a matter of hours.

Perhaps the most significant commitment came from Germany, which on Saturday announced — just before Mr. Zelensky landed in Berlin — that it would send Ukraine 30 additional Leopard tanks and 20 armored fighting vehicles, 16 air defense systems, more than 200 drones and a slew of other arms and ammunition. The leaders of France and Italy also gave vaguer promises to send light tanks, ammunition and air defense systems.

The additional Leopards and infantry fighting vehicles that Germany is sending as part of its package worth 2.7 billion euros, or nearly $3 billion, will be most useful on Ukraine’s southern steppe, where the Russian-controlled terrain, Mr. Kirkegaard said, is well suited “for tank or maneuver warfare.”

But Max Bergmann, the director of the Europe, Russia and Eurasia program at the Center for Strategic and International Studies in Washington, noted that it was not clear that all of the newly-pledged German tanks would arrive soon. (Berlin has already delivered 18 Leopard tanks to Ukraine.)

However, he said, the commitment “helps give Ukraine a degree of confidence” as military planners prepare for a drawn-out battle.

As of early March, only 31 percent of tanks and 76 percent of other armored fighting vehicles had been delivered to Ukraine for the coming counteroffensive, according to classified U.S. military assessments that were recently leaked, although American officials have said far more have been delivered in the months since. The Biden administration has also pledged to send 31 American-made Abrams tanks to Ukraine, but they are not expected to arrive until fall at the earliest.

The new air defense systems that were promised may help ease American worries that Ukraine did not have enough to protect itself as the counteroffensive neared. Four of the 16 air defense systems that Germany has newly pledged are considered among the most sophisticated on the market.

The newly promised long-range Storm Shadow missiles, which Britain pledged on Thursday, help answer a longstanding request from Ukraine. The United States has so far resisted sending American long-range missiles to Ukraine, in part to avoid potentially escalating the war with weapons that Ukraine could use to reach into Russian territory.

Mr. Kirkegaard said the long-range drones that Britain pledged on Monday are of particular threat to the Russian Navy’s Black Sea Fleet in the Crimean port of Sevastopol and other sites in and near Crimea, including the Kerch Strait Bridge that connects occupied Crimea to Russia.

Crimea has been a key staging ground for the Russians operating in captured territory in southern Ukraine.