United States President Joe Biden has announced that the first US-made Abrams tanks will be delivered to Ukraine next week, a crucial delivery at a time when Ukrainian forces are engaged in brutal fighting on the front lines with Russia after months of a slow-moving counteroffensive.

Biden made the announcement on Thursday after meeting with Ukrainian President Volodymyr Zelenskyy in Washington, DC, where the US unveiled a new $325m military aid package for Ukraine.

“Next week, the first US Abrams tanks will be delivered in Ukraine,” Biden said at the White House, alongside Zelenskyy, who was making his second visit to the US since the Russian invasion in February 2022.

This is what we know about the latest US military aid and the significance of the US army’s top tank for Ukrainian forces:

State-of-the-art tank

• The M1 Abrams tank is considered a state-of-the-art weapon and more powerful than many Soviet-era tanks currently operated by Russian and Ukrainian forces.
• Washington originally promised that 31 Abrams battle tanks would be delivered to Kyiv at the start of the year.
• A delivery date for the Abrams was then adjusted with the Pentagon speaking of a date later in the year.
• Washington’s decision to provide Abrams tanks to Ukraine represented a considerable U-turn as US defence officials had repeatedly said that the Abrams were ill-suited for Kyiv’s forces due to the complexity of logistics to keep them supplied with parts, fuel and ammunition, and the complex nature of their operation.

• Sydney Freedberg, a contributing editor of the digital magazine Breaking Defence, told Al Jazeera earlier this year that because Abrams tanks are used significantly less across Europe, Ukraine may struggle to cope with logistic infrastructure such as obtaining spare parts, warehousing and general maintenance. The four-person tank is also complex to operate.
• The US Army Europe and Africa Spokesperson Colonel Martin O’Donnell said last month that 200 Ukrainian servicemen were completing the final phases of training to operate the Abrams tanks, according to the Washington, DC-based think tank, the Institute for the Study of War (ISW).
• The Abrams tanks arriving in Ukraine next week will be paired with 120mm armour-piercing depleted uranium rounds.
• The use of depleted uranium munitions is highly controversial due to the association of such ammunition with health problems, including cancer and birth defects, in areas where they were used in past conflicts.
• Al Jazeera’s defence analyst Alex Gatopoulos has said that the latest-generation main battle tanks, such as the Abrams and the German-made Leopard 2 tanks, are vital for Ukraine to punch holes in Russian defensive lines.

• Southern Ukraine is flat and ideal tank territory. But Russia has spent months building complex defensive fortifications involving deep trenches, huge minefields and reinforced fighting bunkers along its front lines.
• Ukrainian official have consistently referred to the strength of the Russian defensive lines as a key reason for the slow progress of their ongoing counteroffensive.
• The Abrams tanks might be arriving at a key moment in the counteroffensive.
• The ISW reported on Thursday that Ukrainian armoured vehicles are now operating behind the “final line of the Russian defensive layer” in the western Zaporizhia region where Ukraine has penetrated.
• Ukrainian armour appears to have advanced beyond “Russian anti-tank ditches and dragon’s teeth obstacles that are part of a tri-layered defence” in the region, the ISW said, adding that it was the first observed instance of Ukraine’s heavy armour operating beyond the tri-layer lines.

• “The Ukrainian ability to bring armoured vehicles to and through the most formidable Russian defences intended to stop them and to operate these vehicles near prepared Russian defensive positions are important signs of progress in the Ukrainian counteroffensive,” the ISW said.