Hrothgar's hall, Heorot, is endangered twice; first by Grendel, and then by Grendel's mother. Both times, Hrothgar and his council make efforts to defend it.
Grendel terrifies Hrothgar's people the point that Heorot is deserted, and Grendel is said to rule the night. We can assume that fighting Grendel proved useless; he is claimed to be as strong as thirty men. Hrothgar later tells Beowulf that some of his men had claimed they could stop Grendel, only to be found dead the next morning;
Boasted full oft, as my beer they drank,earls o’er the ale-cup, armed men,that they would bide in the beer-hall here,Grendel’s attack with terror of blades.Then was this mead-house at morning tidedyed with gore
Whiles they vowed in their heathen fanesaltar-offerings, asked with wordsthat the slayer-of-souls would succor give them