According to the Ba'alei Tosafos (Da'as Zekeinim 12:4, Berachos 7b), Avraham Avinu made a pilot trip to Eretz Yisroel before making aliya, notwithstanding the fact that his aliya was planned step by step by the Rebbono Shel Olam Himself. The Tosafos are brought to this explanation in order to reconcile their calculations that on the one hand, Avraham was seventy years old at the bris bein ha'besarim, while on the other hand, the opening of our parsha that brings Avraham to Israel at the age of seventy-five. Avraham's first trip, at the age of seventy, is recorded in our parsha and culminates in the vision of the multitude of stars that resemble our people in the future. That trip did not result in a lasting aliya and Avraham finds himself back in his land of origin shortly thereafter. (Rashi and Ramban both take issue with dating the bris bein ha'besarim to have taken place when Avraham was seventy, which requires rearranging our parsha from a simple chronological narrative to one with significant "flashbacks", and the Netziv (15:7) vigorously defends their view in his commentary on Chumash.)
Avraham's aliya at age seventy, as described by the Ba'alei Tosafos, was presumably to get away from his pagan Babylonian environment. That aliya climaxed with the covenant, but only to see Avraham then return to chutz la'aretz. Our parsha opens with Avraham being commanded to make aliya again, but this time as a person who has a treaty with G-d and who is returning to his Divinely promised homeland. The Chareidim (a 15th century commentary) explains that the pattern of the two aliyot will match the causes of immigration by Avraham's offspring. At times we will come to Israel running for refuge, trying to escape the precariousness of the exile, and sometimes we will simply return home proudly bearing a divine treaty.
Nevertheless, one question still remains: why did Hashem record the bris bein ha'besarim as a flashback, after a battle, and not in chronological order at the beginning of Lech Lecha?
It seems to me that by placing it after the battle, the promise and zechuyos of the seventy-year-old Avraham are boldly apparent, and Hashem's choosing Avraham as a covenantal partner is well understood without any commentary or conversation. The covenant was made when he was seventy because Hashem saw in him a person who would risk everything to bring back his estranged nephew from captivity, a person who would understand well the promise and the responsibilities of being a covenantal partner with the Creator.
This insight breathes life into one of the many impressive wartime thoughts of the saintly giant HaRav Avraham Yitzchak Kook zt"l. In an essay on war that he penned during World War One, published in Orot, he explains why Chazal refer to Hashem as ba'al milchamot - the Master of war. With great trepidation of finding any positivity in something that creates unending pain and suffering, Rav Kook points out that nations define themselves during war. Sadly, wars determine a nation's highest values and defining missions.
We see from the current war in Eretz Yisroel that our nation defines itself around finding safe-haven for our people and protecting our G-d-given land while simultaneously protecting all life. Avraham, in similar fashion, defined himself to be responsible for his nephew while simultaneously confident in Hashem's vision.
Finally, the Jewish people have had battles in the times of Yehoshua and in our own times that miraculously showed the bond between Hashem and His children. Let us all try to do the teshuva incumbent upon us so that we will once again merit to see miracles.