We see from the beginning of the chapter that God addresses this prophecy to "Mount Seir" (Ezekiel 35:1-2), which is an alternative name for Edom, descendants of Esau and cousins of the Israelites. About a thousand years before this prophecy, the family of Esau had migrated from Canaan southeastward into the rugged wilderness area beyond the Dead Sea (Genesis 32:3). Here, the people of Seir lived, and within a short time, the two families had merged into the nation of Edom. There is an indication that "Mount Seir" may specifically refer to Edom's central leadership (see verse 15).
From the beginning, the Edomites harbored a brooding hatred for their uncle Jacob's descendants, whom we know as the children of Israel. Clearly, the original bone of contention was Jacob's stealing of the patriarchal blessing from Esau (Genesis 27), as well as his procuring of the birthright for a song when Esau was desperate for food (Genesis 25:29-34). The two branches of the family have been in near-continual conflict ever since. The first people to harry the Israelites as they came out of Egypt were the Amalekites, one of the clans of Esau's line (Exodus 17:8-16), and at the end of that battle, Moses prophesies, "[T]he LORD will have war with Amalek from generation to generation" (Exodus 17:16).
As Israel approached the Promised Land nearly forty years later, Moses asked permission of the Edomites to pass through their land, but they refused (Numbers 20:14-21). As the generations passed, the two fought sporadically, and Edom invariably sided with Israel's enemies in other actions. The Edomites earned the reputation of taking advantage of Israel or Judah when they were down, raiding and plundering in the wake of military defeats. Through Amos, God castigates the Edomites, "I will not turn away its punishment, because he pursued his brother [Israel] with the sword, and cast off all pity; his anger tore perpetually, and he kept his wrath forever" (Amos 1:11).
This is the background of Ezekiel 35. When the Babylonian army under Nebuchadnezzar attacked and conquered Judah, destroying Jerusalem and the Temple and deporting thousands of Jews to Babylon, the Edomites allied themselves with the Chaldeans. God mentions this in verse 5: ". . . you . . . have shed the blood of the children of Israel by the power of the sword at the time of their calamity, when their iniquity came to an end. . . ." Their perfidious activity at this time is detailed in the book of Obadiah.
Thus, because the Edomites were so eager to shed blood—"since you have not hated blood," as God understates it—they would have to experience their blood being shed. God would set them up—"I will prepare you for blood"—to be conquered and laid waste in punishment for their atrocities against His people. He promises, "I will make you perpetually desolate, and your cities shall be uninhabited; then you shall know that I am the LORD" (verse 9). Soon thereafter, their "ally" Nebuchadnezzar took over their lands as he had done to Judah (see Jeremiah 27:3, 6), and it was not long before the Nabateans pushed them out of their ancestral homeland and into southern Judea, where they remained a subject people.