As seen in Beowulf, why is Hrothgar's lieutenant concerned about the arrival of Beowulf and his men?
In Beowulf, in Chapter Three, there are several men at the story's beginning that show concern over the arrival of Beowulf and his men.
The first man is set to keep watch over the Danish shore to guard Hrothgar's kingdom; he is concerned with the Geats' arrival for several reasons.
First, the men have landed openly in full battle gear. They obviously are an impressive and evening frightening sight. The Geats are strangers in this land, so the lookout is concerned for the safety of Hrothgar and his people, wondering if the men are enemies. Second, those who know Hrothgar have knowledge of a "word of passage" (or password) that they must use to gain welcome onto this Danish coastland—a word which Beowulf and his men do not have. The scout announces:
Who then are you, men bearing arms and clad in coats of mail, who have thus come with this mighty vessel over the ocean's ways? I have been set as a sentinel over this seacoast that no foe of the Danish folk should harm the land with marauding ships. Never have shield-bearing men so openly landed, nor do you know our clan's word of passage, or hold my folk's consent—never have I seen in the world a warrior like that one among yourselves—a hero in his armor!
Beowulf is obviously a warrior unlike any the lookout has seen before: Hrothgar's scout comments on the mighty Geat's appearance and the manner in which he holds himself—like a king. The scout continues:
He is no henchman, unless his looks deceive; he has a regal bearing. Now must I know your nationality before you wander hence from here as intruders in Danish lands. Now, foreigners who fare on the ocean, hear me out: it's best to make haste and let me know from whence you come.
Finally, Hrothgar's scout needs to know their identity—what clan or tribe they are a part of—so that he can ascertain whether or not it is safe to allow them to disembark from their ship. There is a warning in his comment as he advises them to "make haste" in identifying who they are.
In Chapter Four, Beowulf establishes who he and his men are, offering (if, he notes, the stories they have heard of Grendel are true) to aid Hrothgar to fight off the beast and so the Danes can live in peace once more. Having heard Beowulf's words, the scout instruct the men to proceed to Hrothgar's mead hall, armed—thereby expressing his faith in their peaceful intentions.
In Chapter Five, as Beowulf's men take their seats in the great hall waiting for permission to see Hrothgar, another Dane addresses them, wondering who they are: his name is Wulfgar, Hrothgar's "herald and marshal."
A proud warrior there questioned the heroes about their home and kinsmen: “Whence do you bear these burnished shields, gray armor, and grim helmets, and a multitude of spears? I am Hrothgar's herald and marshal. Never have I met so many foreigners of heroic bearing. Methinks that it's for glory—not because of exile, but for courageous valor—that you seek Hrothgar!”
Once again, this man is concerned about who these men are; but he also assumes (by their bearing) that they are not criminals ("exiles"), but fine warriors. He, too, must be concerned for their intentions before he seeks out Hrothgar. He believes they are no danger—that they are there only for "glory" and "for courageous valor;" so Wulfgar approaches Hrothgar, encouraging the king to meet with Beowulf and his men. Hrothgar announces that he knew Beowulf's father in his younger days, and so Wulfgar invites the Geats into Hrothgar's presence. In allowing them to wear their armor, he (like the scout before him) demonstrates his trust of them.
While the scout and Wulfgar take their measure of the Geats and find them worthy of praise and respect, in Chapter Eight, Unferth, son of Ecglaf, tries to start a quarrel with Beowulf. His concern is born first of jealousy for...
...he always begrudged other men who might achieve more fame under heaven than he himself.
While Unferth tries to start trouble and question some of Beowulf's feats of bravery, the mighty Geat easily puts the other man in his place, noting that what Unferth says must be the result of drunkenness because of the beer he has had. In speaking out, Unferth issues a challenge of Beowulf's abilities. However, while Beowulf is a mighty warrior (which proves his physical prowess), he is also an excellent example of a man skilled in speaking and "thinking quickly on one's feet"—something also valued, which proves one to be a intelligent warrior and hero. Unferth is no match for the wise, valiant and experienced Beowulf.
Of the Danes Beowulf and his men first meet upon arriving in Hrothgar's land, all three issue challenges. The first two men want to be assured of Beowulf's honorable intentions. The last (Unferth) challenges Beowulf's meddle as a warrior. Beowulf puts all of their concerns to rest.
As Beowulf and his men arrive on Hrothgar's lands (in the epic Beowulf), the Scylding scout (or Hrothgar's lieutenant) is concerned. The men, "with war-gear in readiness," land upon the shore unannounced. The Danes knew nothing of the Geats' arrival or of their intentions upon the Danes' land.
The scout states that he has never in his life seen men arrive upon Hrothgar's lands so openly or wonderfully armored. He immediately recognizes Beowulf's greatness and the nobility of the warrior. The presence of the men is, essentially, overwhelming, and the scout demands that the men tell him why they are there.
Not only is the scout in awe of the men, each man Beowulf and his thanes approach immediately recognize their greatness. Although not as concerned as the lieutenant, Beowulf and his men arrive in full battle dress (so as to visually speak to their intent to defeat Grendel).