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This page mentions and I quote:
The A7V would be involved in the first tank vs. tank battle of the war on April 24, 1918 at the Second Battle of Villers-Bretonneux β a battle in which there was no clear winner.
Then if we look at operational History of the A7V tank, we get a brief overview of the Battle:
The first tank against tank combat in history took place on 24 April 1918 when three A7Vs (including chassis number 561, known as "Nixe") taking part in an attack with infantry incidentally met three Mark IVs (two female machine gun-armed tanks and one male with two 6-pounder guns) near Villers-Bretonneux.
During the battle, tanks on both sides were damaged.
According to the lead tank commander, Second Lieutenant Frank Mitchell, the female Mk IVs fell back after being damaged by armour-piercing bullets. They were unable to damage the A7Vs with their own machine guns.
Mitchell then attacked the lead German tank, commanded by Second Lieutenant Wilhelm Biltz, with the 6-pounders of his own tank and knocked it out.
He hit it three times, and killed five of the crew when they bailed out. He then went on to rout some infantry with case shot. The two remaining A7Vs in turn withdrew.
The page for German commander in the Battle gives a little more information:
During the battle his tank encountered a group of three British Mark IV tanks β two "female tanks", armed only with machine guns and a single "male tank", armed with 6-pound guns.
Both the British female tanks were damaged and retreated, as their machine guns had no effect on Blitz's A7V. In a running battle that followed, both tanks manoeuvred to avoid the other's fire while lining up on their opponent. Biltz's tank lost the duel β it was hit three times by the British tank and heeled over on its side. The crew abandoned their A7V but five were killed by continued fire from the Mark IV, which went on to engage two more A7V tanks that had appeared on the scene.
Biltz's men were able to recover their damaged tank later.
The battle itself didn't end after this duel.
As Mitchell's tank withdrew from action (To engage German infantry), seven Whippet tanks also engaged the infantry. Four of these were knocked out in the battle, and it is unclear if any of them engaged the retreating German tanks. Mitchell's tank lost a track towards the end of the battle from a mortar shell and was abandoned.
The engagement would be called indecisive because:
Neither side decisively defeated the other side. However one could give slight advantage to the British purely on the ground that theirs was the last Tank standing on the field, when one of the A7Vs was knocked out and two were forced to retreat.