Mercilessness characterized by an unwillingness to relent or let up

Usage examples of relentlessness.

Though they were undoubtedly a minority in the relentlessness of their revolutionary convictions, the militants were capable, on days of crisis, of mobilizing armed crowds of tens of thousands.

Although their slow stagger was obviously no match for that of the van, the relentlessness and pointless persistence of the rotting gathering caused an icy chill to run the entire length of his spine.

Clever writers about the Reds of the West have told how they rode, and how they ambushed, and of their relentlessness, but not one story shows that they had the bushcraft the equal of that of the Australian aborigine.

As they stepped on to the highroad from their plank bridge, and looked round at the endless monotony of levels, the land a little darker than the sky, the sea sounding small beyond the sandhills, his heart filled strong with the sweeping relentlessness of life.

Instead, mind-numbingly immense fleets had advanced in dead silence, indifferent to losses, grinding the defenses of one system after another to powder with a nonfeeling relentlessness even more horrible than Rigelian malevolence.

However alluring its colors were, however satisfying its geometries and exquisite its details, the city was the work of a collective madness: a compulsive vision that had refused to be placated until it had covered every inch of the Dominion with monuments to its own relentlessness.

I suppose I find these moments precious and reassuring because they take place outside me, outside the silent grid, because they suggest an outer state that works somewhat the way my mind does but without the relentlessness, the predeterminative quality.

But India's strategic position is so exposed, and China's relentlessness in conquest is so well known, that you must know both courses of action are futile.