EXPLAINER: Why the US flipped on sending tanks to Ukraine

WASHINGTON For months, U.S. officials balked at sending M1 Abrams tanks to Ukraine, insisting they were too complicated and too hard to maintain and repair.

On Wednesday, that abruptly changed. Ukraine's desperate pleas for tanks were answered with a sweeping, trans-Atlantic yes.

The dramatic reversal was the culmination of intense international pressure and diplomatic arm-twisting that played out over the last week. And it resulted in in a quick succession of announcements: The U.S. said it will send 31 of the 70-ton Abrams battle tanks to Ukraine, and Germany announced it will send 14 Leopard 2 tanks and allow other countries to do the same.

A look at the massive battle weapon, why it is important to Ukraine's war with Russia, and what drove the Biden administration's tank turnabout.

WHAT ARE THE ABRAMS?

M1 Abrams tanks have led American battle assaults for decades.

Carrying a crew of four, the Abrams was first deployed to war in 1991. It has thick armor, a 120 mm main gun, armor piercing capabilities, advanced targeting systems, thick tracked wheels and a 1,500-horsepower turbine engine with a top speed of about 42 miles per hour (68 kilometers per hour).