The first berakha of the Amida is known as 'abot' (ancestors) and it refers to God's protection of the Jewish people. In this berakha we don't ask for protection: we praise God stating that our miraculous survival as Jews, is due to His eternal divine protection.
We mention that haShem Almighty protected Abraham, Ytzchak and Yaakov (E-lohe Abraham, etc). We also describe with a few words what we can 'humanly' grasp of God's protective power (hagadol, hagibbor, etc.), a power that God uses to bestow kindness (gomel chasadim tobim).
We state that because of the merit of our ancestors (zokher chasde abot), God grants us His present and future salvation (umebi go'el).
God protects us because He so promised (lema'an shemo) our ancestors, and because He loves us (beahaba). To understand these two last concepts you must read the Pasuk Debarim 7, 7.
Finally we state that God is our King (melekh), but a special kind of king: not the king that demands for his own sake, but a King ready to help when we ask (ozer) and to rescueus when we are in trouble (moshi'a) and a king who covers us with His invisible shield (magen) against harms and hazards we are not aware of.
Magen is indeed the highest level of divine protection.
The protection responsible for the survival of the Jewish people since the time of Abraham Abinu (baruckh ata hasem magen Abraham).
Rabbi Yosef Bitton. YMJC 130 Steamboat Rd. Great Neck NY 11024