Last June, Joe Biden reportedly snapped at Ukrainian President Volodymyr Zelensky over the phone, raising his voice in indignation.
At issue was the amount and nature of U.S. aid being dispatched to repel the invading Russian forces.
According to NBC, "Biden had barely finished telling Zelensky he'd just green-lighted another $1 billion in U.S. military assistance when Zelensky started listing all the additional help he needed and wasn't getting."
At that point, Biden told the Ukrainian president he should be more grateful for the work he'd been doing - overcoming increased political opposition that threatened to undermine U.S. support.
The frustration had been building for weeks, as Zelensky had repeatedly (and publicly) complained that aid wasn't arriving quickly enough.
So this time, Zelensky responded with a new show of public appreciation through videotaped remarks.
"I had an important conversation with U.S. President Biden today," he said. "I am grateful for this support. It is especially important for our defense in Donbas."
Seemingly, it was a watershed moment for the two leaders, and their relationship has only improved since then.
But what hasn't changed is Ukraine's endless appetite for foreign military aid.
And this week, the embattled country landed another big score in the form of tanks.
The United States is now preparing to send M1 Abrams tanks to Ukraine, while European nations are ready to dispatch German-made Leopard 2 tanks.
It's yet another milestone in aid escalation after the United States responded to Zelensky's pleas for midrange missile systems by sending HIMARS (High Mobility Artillery Rocket Systems) last fall.
The HIMARS were a game-changer, and, obviously, the tanks will be too.
They could be a key component of a spring counteroffensive, helping breach lines of Russian-dug trenches.
They'll also make quick work of their Russian counterparts, which are mostly ineffectual holdovers from the Soviet era. Those that are able to function (which may be only one-tenth of Russia's fleet) are poorly outfitted and increasingly understaffed.
And yet they're still not enough.
Dozens or even hundreds of new Western tanks will not be enough to swing this war decisively in Ukraine's direction.
And that's why Ukrainian officials already have an eye toward their next big get - F-16 fighters.
"We will get F-16s," Yuriy Sak, an adviser to Ukraine's Defense Minister Oleksiy Reznikov, told CNBC. "At the moment, more than 50 countries around the world have this platform. I don't see a reason, or any rational explanation, why Ukraine shouldn't be getting F-16s or other fourth-generation jet fighters."