More Abraham

Here's an extended comment on that same verse:

וַיְהִ֗י בְּשַׁלַּ֣ח פַּרְעֹה֮ אֶת־הָעָם֒ וְלֹֽא־נָחָ֣ם אֱלֹהִ֗ים דֶּ֚רֶךְ אֶ֣רֶץ פְּלִשְׁתִּ֔ים כִּ֥י קָר֖וֹב ה֑וּא כִּ֣י ׀ אָמַ֣ר אֱלֹהִ֗ים פֶּֽן־יִנָּחֵ֥ם הָעָ֛ם בִּרְאֹתָ֥ם מִלְחָמָ֖ה וְשָׁ֥בוּ מִצְרָֽיְמָה׃

And it came to paſſe when Pharaoh had let the people goe, that God led them not through the way of the land of the Philiſtines, although that was neere: For God ſaide, Leſt peraduenture the people repent when they ſee warre, and they returne to Egypt.

[See, tagin on the final mem.]

What does it mean, "when they see war"? Our commentator writes:

בראתם מלחמה. אותה מלחמה שעשו פלשתים עם בני אפרים שהרגום כשיצאו ל' שנה קודם הקץ, שנאמר: והרגום אנשי גת הנולדים בארץ. וזהו בראותם מלחמה.

בראתם, תגין: אותה המלחמה שכתוב בדברי הימים, שנאמר: והרגום אנשי גת

בראותם: מ' שנה הלכו במדבר. ועכשיו אם היו רואין היו וחזרין מיד למצרים, בׄרׄאׄתׄ םׄ: ו' מאות אלף אם היו רואים, וזהו בראות מ

בׄרׄאׄתׄ םׄ: ת' אברם. לאברהם נאמר כי גר יהיה זרעך ת' שנה, ולא סיימו עדיין כשיצאו בני אפרים ולכך הכום פלשתים כי עדיין לא היה (לכם) [להם] לצאת. ושמא כך היו עושין לישראל. וזהו בׄרׄאׄתׄםׄ: אברם ת: ומלידת יצחק היו ת' ואותם מנו מברית בין הבתרים ואז היה הברהם בן ע' שנה

When they see war. That war which the Philistines had waged against the Ephraimites, killing them when they left [Egypt] 30 years before the Designated Time, as it is written: [...] whom the men of Gath, that were borne in that land slewe (I Chron. 7:21). And this is what our verse means when it says that the Israelites might see war.

When they see (bir’otham). There are tagin on the [final] mem to indicate that this refers to that specific war mentioned in Chronicles.*

When they see (bir’otham). [The tagin on the mem] refer to the 40 years during which they would travel in the wilderness, [in accordance with the numerical value of mem, namely 40. If they would see war now, they would return immediately to Egypt: בראות מ.** If the 600,000 would see -- this is בראות מ.

When they see (bir’otham). [The letters of בראתם are an anagram of] אברם ת, Abram 400. For Abraham had been told that his descendants would be sojourners for 400 years, and this time had not been completed when the Ephraimites attempted to leave Egypt, and that is why they were slain by the Philistines, for they should not have left yet. And lest [you think] that this would happen [now] to the Israelites, [Scripture tells us]: בראתם, Abram 400, [that is, Abraham's 400 years were now up, so there was no need to worry]. The count of 400 begins at Isaac's birth***, but [the Ephraimites] calculated it from the time of the Covenant Between the Pieces [when the prophecy was told to Abraham], which was when Abraham was 70 years old, [thirty years before Isaac's birth].

*I don't get this, exactly. How do the tagin on the final mem allude to the war mentioned in Chronicles? Perhaps these are hyperlink tagin, referring to a similarly-adorned mem in the Chronicles passage? If so, when I order my scroll of Chronicles, I should have the final mem of והרגום adorned with tagin.
**I really don't get what's going on here. What do the forty years of wilderness wandering, which haven't happened yet, have to do with the problem of seeing (evidence of the old) war now? Is the idea that if the Israelites are scared by seeing the bones of their Ephraimite brethren, and thus return to Egypt, they will forfeit the entire upcoming forty years? But why specifically forty years -- couldn't they have another Exodus a year later, or a hundred years later, or never? And why the reference to 600,000. Of course, that's the (rounded) number given for the male able-bodied Israelites during the wilderness years, but is their some kind of gematria that is flying over my head?
***This is the standard calculation: The 400 years in which "Abraham's seed" would be "sojourning" starts from the birth of Isaac, 30 years after the Covenant Between the Parts, because Abraham doesn't have any (relevant) "seed" until Isaac. The 430-year figure given in Exodus 12:40 is considered to begin at the time of the Covenant itself. Either way, only 210 of the years are spent in Egypt.