The ancient city of Arad, today called Tel Arad (a national park in Israel) is on the line from Beer-Sheva to the Dead Sea in the eastern Negev, approximately 32 kilometers from Beer-Sheva, and 28 kilometers from the Dead Sea. (Modern day Arad is 9 kilometers east of Tel Arad.) Tel Arad is located along the river bed known today as Nahal Beer-Sheva, which continues past Beer-Sheva, joins Nahal Besor and ends by the Mediterranean Sea in Gaza. Is this the Arad being referred to in Bemidbar 21:1-3?
Yohanon Aharoni (1976) notes that there are two other ancient cites on the river bed between Beer Sheva and Tel Arad, Tel Masos and Tel Malhata. He argues that Tel Masos is the place called Horma in 21:3 and Tel Malhata is the Arad referred to in 21:1, while Tel Arad is the Israelite Arad of a later period. Alternatively, Naaman (1983) suggests that Horma is in the western Negev, which would mean that it was not so close to Arad, which was in the eastern Negev. However, with all these possibilities, both Arad and Horma were situated on the southern border of the land of Israel. Thus, after the people attempted to enter the land of Israel on their own after they heard the punishment for not wanting to enter the land of Israel, they were thrown back to Horma, outside the southern border of the land of Israel, 14:40-45.
One problem with the archaeological findings is that there does not seem to be any evidence that either Tel Arad or Tel Malhata was populated in the years when it is believed that the Jewish people left Egypt, approximately 1400-1300 BCE. Aharoni writes that Tel Malhata was populated from 1800-1570 BCE and then again starting in the 1200s BCE. While new finds might refute this dating, if this is correct, then who was the king of Arad who fought the people in the desert if Arad was not populated?
Aharoni quotes N. Glueck that the king of Arad was a "Bedouin" type sheikh who controlled the area. According to this idea, even after the city Arad has been deserted, the name remained in the area. The tribes who lived in the area were referred to by the name Arad, even though they did not live in the city. This hypothesis correlates with Chazal's (see Rashi on 21:1) suggestion that Arad here refers to Amalek, as they were tribes that wondered in the Negev, and did not live in one fixed area. (Note if this approach is correct, this does not preclude the existence of other Amalek tribes, as for example the book of Joshua 12:14 records that Yehoshua again captured the area.)
Why did the king of Arad attack the Jewish people? Why was he not scared of the Jewish people after the miracles of the Exodus? Chazal (Rosh Hashanah 3a, Rashi on 21:1) explain that the king heard that the clouds of glory, which protected the people, disappeared, and hence it was possible to attack the people.
N. Leibowitz (1982, pp. 255-259) notes that the Ramban and Ibn Ezra (based on the Targum) explain that the word Atarim refers to the spies who Moshe had sent in the 2nd year. She suggests that the people "had shown their lack of confidence and fear of the future by sending the spies…. The result was that the Canaanite inhabitants lost their dread of the Chosen People and attacked them at the first opportunity." I doubt this approach since sending spies is a perfectly acceptable course of action, especially from the point of view of the King of Arad, but I agree that this battle is related to the incident of the spies.
After the people heard that they were doomed to be in the desert for 40 years due to their acceptance of the spies' report, they had attempted to enter the land of Israel on their own, where they were roundly defeated by Amalek and the Canaanites, 14:40-45. Now, 38 years later, the march to Mount Hor, 20:22, brought the people close to the area where they had attempted to enter the land of Israel on their own 38 years earlier. The Jewish people were not going to enter the land of Israel from the south but were going to turn back after the digression to Mount Hor in order to enter Israel from the eastern side of the Jordan River, but the king of Arad did not know this information. Presumably he also did not know that the earlier invasion after the sin of the spies was against G-d's wishes. Instead, 21:1 records that he was informed that the Jewish people were traveling in an area close to him. The inhabitants of the land must have been suspicious that the Jewish people would attempt a new invasion after the first invasion had failed, and they would have been on alert when the Jewish people returned to the area. The king of Arad thought that the Jewish people were attempting to invade the land of Israel again, as they had endeavored 38 years earlier. Once he thought that he was going to be invaded, then his best defense was to attack. He was not afraid of the Jewish people since he and/ or his people had defeated them 38 years earlier.
The decision by the king of Arad to attack surprised the Jewish people and his army succeeded in taking some of the people captive. However, the Jewish people were able to re-group. 21:2 records that the people made a vow to G-d as a prayer for G-d to assist them. And, 21:3 records that G-d heard the people's prayer and the Jewish people defeated the Canaanites. What is the significance of this battle? Why is it recorded in the Torah?
The victory not only removed the stain of their previous defeat 38 years earlier, but more importantly the actions of the people give an indication as to why this new generation was worthy of entering the land of Israel, as opposed to the first generation. Initially, the king of Arad succeeded with his surprise attack, but the people did not whine or complain to Moshe. Instead, they made a vow to G-d, counter-attacked without knowing that G-d would perform any miracles for them, and fulfilled their vow.
In addition, with their victory they had broken through the southern border of the land of Israel, and all they had to do was to march north to arrive at the land of Israel. However, G-d wanted the people to enter Israel from modern day Jordan, just as Avraham and Yaakov had done (Bereshit 12:6, 33:18), and hence the people had to retreat and cross back into Jordan. The people did this, 21:4, which shows how they listened to G-d. This marching up and down the Negev/ Arava was probably a test of the new generation to see if they would follow G-d’s commands. For the most part they passed this test, as they did not attempt to enter Israel the easy way against G-d’s commands. The second generation was not perfect (and who is?) as they still complained, 20:2 and 21:5, but their actions signaled their maturity that they were ready to go into the land of Israel.
Bibliography:
Aharoni, Yohanon (1919-1976), 1976, Nothing early and nothing late: Re-writing Israel's conquest, The Biblical Archaeologist, 39:2, pp. 55-76.
Leibowitz, Nehama, 1982, Studies in Bemidbar, translated and adapted by Aryeh Newman, Jerusalem: The World Zionist Organization.
Naaman, Nadav, 1983, The Inheritance and Settlement of the Sons of Simeon in the South of Eretz Israel (Hebrew) in Isac Leo Seeligmann volume: Essays on the Bible and the ancient world, vol. 1, edited by Alexander Rofe and Yair Zakovitch Jerusalem: E. Rubinstein, pp. 111-136.