Ukraine wants heavy weapons. What NATO countries send now will shape the war.

But in the United States and Europe, the discussions over what types of weapons to send are far different from what they were just six weeks ago.

This is a pivotal moment of the war, and as the battlefield shifts, the sorts of weapons Ukrainian forces need are changing, too. There is no longer a fear that the Ukrainian capital, Kyiv, could fall within days. Russian forces are repositioning for a fight over eastern Ukraine — what many predict will be full-scale confrontation on flat, open, rural terrain, between infantry, armor and artillery, in the kind of engagements not seen in generations.

Battles may be tougher for Ukrainians as war shifts to wide-open terrain in east

On Saturday, Britain’s Prime Minister Boris Johnson made a surprise visit to Kyiv to meet with Zelensky. His main message was about weapons: that Britain would supply 120 more armored vehicles, in addition to anti-ship missile systems to support Ukraine in the Black Sea.

This next phase of war in Ukraine could be “protracted” — “measured in months or longer,” national security adviser Jake Sullivan warned at a White House briefing. It could look like something from World War II, with two large armies facing off, Kuleba told NATO foreign ministers earlier this week.

“To win such a war, we need different help than what we have been receiving before,” said Ukraine’s defense minister, Oleksii Reznikov, in a video appeal released Thursday. “We want to liberate the enemy-occupied territories as soon as possible. To do this, we need other weapons.”

In the early days of fighting, NATO countries worried that the weaponry they gave to Ukraine might be quickly captured by superior Russian forces, or that Ukrainian troops did not have the time to train to use new equipment effectively, or that sending offensive weapons would escalate the conflict and enrage Russian President Vladimir Putin, who was rattling his nuclear sword.

Weapons are easier to give than to take back.

But as the war has gone on, those concerns have begun to recede. Now, some NATO countries are preparing to supply Ukraine with more lethal, sophisticated, long-range and heavily armored weapons.

The question is whether those will come as fast as Ukrainian officials want — to stop Russia’s advance and push out Russian troops.

What do Ukrainian forces need?

Since the Feb. 24 invasion, Western governments have supplied Ukraine with billions of dollars worth of weapons, including thousands of easy-to-use, shoulder-fired missile systems, which proved especially deadly, in the hands of small Ukrainian commando groups, in slowing, stopping and then reversing the Russian assault on Kyiv.

These “shoot-and-scoot” launchers were decisive, according to military analysts. “We know that military assistance is having a critical impact on this conflict,” Sullivan said Monday, highlighting the U.S.-produced, shoulder-fired antiaircraft Stingers and antitank Javelins that have been shipped to Ukraine.

Javelins, not jets: How the U.S. is arming Ukraine against Russia

Now, as the war pivots to the east, the numbers and types of weapons supplied by the United States and Europe will again prove critical for Ukraine. Its forces need to quickly rebuild, to replace equipment lost in six weeks of fighting and to supply the reserve units that the Ukrainian military is now trying to put into the field. They also need to prepare for a new sort of war, with the ultimate aim of not only defending cities but also turning out Russian forces.

“So antitank missiles alone are not going to cut it,” said Michael Kofman, research program director in the Russia Studies Program at CNA, a think tank based in Arlington, Va.

Kofman estimated that Ukraine needs “hundreds” of armored combat vehicles, including tanks, and a tremendous amount of ammunition.

Reznikov ticked off a longer list: air defense systems and combat aircraft to protect citizens and Ukrainian troops from missiles and airstrikes; long-range artillery to keep Russian forces at a distance; tanks and armored vehicles to break through Russian defenses and liberate the occupied territories; and anti-ship missiles to beat back the Russian naval siege and unblock ports on the Black Sea.

Western governments have been reluctant to send such heavy weaponry. But the Czech Republic has become the first NATO country to contribute tanks, a senior Czech official confirmed to The Washington Post on Saturday, speaking on the condition…