From EVE History
Minmatar NPC faction.
The Defiants is a military unit composed of ex-Minmatar navy personnel that followed Karishal Muritor when he chose to abandon the Minmatar Navy and start open attacks on the Amarr Empire. They held one first campaign of long supported attacks on the Bleak Lands, The Bleak Lands Campaign, that came to an end when their leader was murdered by the Minmatar. They left Amarrian space and remained silent for months.
Months later they returned to the Bleak Lands to start a second campaign directly against the 7th Imperial Navy, "the Saracens", with the support of many other Minmatar corporations. Still, this war cost them dearly (same to the Imperial Fleet) and finally they had to briefly retreat from combat.
But it was indeed brief, little more than a week later the Minmatar Republic invaded the Amarr Empire directly, starting the Empire War. After their defeat against Jamyl Sarum, they retreated, and The Defiants made their last stand in The Bleak Lands in order to gain some time for the Minmatar fleet to retreat. They were crushed by the Empire as a price, and few of them remain alive after that.
They are known to be close allies and friends of the Ushra'Khan Alliance.