וַיִּצְעֲק֣וּ אֶל־יְהוָ֗ה וַיָּ֨שֶׂם מַֽאֲפֵ֜ל בֵּינֵיכֶ֣ם ׀ וּבֵ֣ין הַמִּצְרִ֗ים וַיָּבֵ֨א עָלָ֤יו אֶת־הַיָּם֙ וַיְכַסֵּ֔הוּ וַתִּרְאֶ֙ינָה֙ עֵינֵיכֶ֔ם אֵ֥ת אֲשֶׁר־עָשִׂ֖יתִי בְּמִצְרָ֑יִם וַתֵּשְׁב֥וּ בַמִּדְבָּ֖ר יָמִ֥ים רַבִּֽים׃
他們向永恆者呼求，祂就使黑暗隔在你們和埃及人中間，又使海水臨到他們，淹沒了他們。你們親眼看見我在埃及所行的事。你們在曠野住了許多日子。
Rashbam
ויסע מלאך האלוקים, the one that was guiding the pillar of cloud and the column of fire respectively in front of the marching columns of Israelites, changed positions and moved behind the columns of marching Israelites instead.
Rashbam
ויסע עמוד הענן מפניהם ויעמוד מאחריהם, this was the result of the angel repositioning himself. The purpose of the angel’s move now was to create a barrier between the Israelites and the Egyptians approaching from behind. The angel created a barrier of darkness, impenetrable to artificial means of lighting up the area in front of the Egyptians. (as described in Joshua 24,7). As a result, the Egyptians did not draw nearer to the Israelites during the entire night.
Chizkuni
ויבא בין מחנה, “he positioned himself between the camp, etc.” the Torah refers to the cloud that was controlled by the angel taking up position between the two camps. We encounter something similar in Joshua 24,7: וישם מאפל ביניכם ובין במצרים ויבא עליהם את הים, “He placed darkness between you and the Egyptians and He brought the sea upon them.” (Joshua’s parting speech to the people before they dispersed to their respective portions of the Holy Land.)