BESIEGE : To attack with an army; To surround the enemy with military forces and to cut them off from help or supplies: To surround (a fortified area, esp a city) with military forces to bring about its surrender; crowd round; hem in.
Psalms 139:5 “You hem me in, behind and before; you have laid your hand upon me.”

THE ANGELS of Psalm 91:11
Heavenly host (Hebrew: צבאות sabaoth or tzva’ot, “armies”) refers to the army (Luke 2:13) of angels mentioned both in the Hebrew and Christian Bibles, as well as other Abrahamic texts.
“Heavenly host” is a military term to describe a fighting unit. Ephesians 6 reminds us that we are in a war “against the rulers, against the authorities, against the world powers of this darkness, against the spiritual forces of evil in the heavens” (6:12)
His angels; those blessed, and powerful, and watchful spirits whom God hath appointed to mind the affairs of this lower world, and to take care of the heirs of salvation, Hebrews 1:14. (Matthew Poole Commentary)

Created spirits, so called, made by The LORD, and are at His command; who are ministering spirits to His people, who encamp about them, and are concerned in the preservation of them; they being committed to their care and charge by Him who is Lord of heaven and earth. (Gill’s Exposition)

The first of only two angels mentioned by name in scripture is Michael the Archangel. He is God’s chief warrior (Daniel 10:13,12:1; Revelation 12:7). Some have wings and some appear just like humans (Isaiah 6, Exodus 3).

“For by Him all things in heaven and on earth were created, things visible and invisible, whether thrones or dominions or rulers or powers – all things have been created through Him and for Him.” (Colossians 1:16). The thrones, dominions, rulers, and powers speaks of various orders of angels. Their organization is like that of an army. “For day by day men came to David to help him, until there was a great army like the army of God.” (1 Chronicles 12:22). (BlueLetterBible)

“They are the bodyguard of the princes of the Blood Imperial of heaven, and they have received commission from their Lord and ours to watch carefully over all the interests of the faithful. When men have a charge they become doubly careful, and therefore the angels are represented as bidden by God himself to see to it that the elect are secured. It is down in the marching orders of the hosts of heaven that they take special note of the people who dwell in God. It is not to be wondered at that the servants are bidden to be careful of the comfort of their Master’s guests; and we may be quite sure that when they are specially charged by The LORD himself they will carefully discharge the duty imposed upon them.

“To keep thee in all thy ways.” To be a body-guard, a garrison to the body, soul, and spirit of the saint. The limit of this protection “in all thy ways” is yet no limit to the heart which is right with God. It is not the way of the believer to go out of his way. He keeps in the way, and then the angels keep him. The protection here promised is exceeding broad as to place, for it refers to all our ways, and what do we wish for more? How angels thus keep us we cannot tell. Whether they repel demons, counteract spiritual plots, or even ward off the subtler physical forces of disease, we do not know. Perhaps we shall one day stand amazed at the multiplied services which the unseen bands have rendered to us. (Treasury of David Commentary)

“Be not forgetful to entertain strangers: for thereby some have entertained angels unawares.” Hebrews 13:2

“Are they not all ministering spirits, sent forth to minister for them who shall be heirs of salvation?” Hebrews 1:14

“A thousand may fall at your side, And ten thousand at your right hand; But it shall not come near you.” Psalm 91:7

“Because you have made The LORD, who is my refuge, even the Most High, your dwelling place, No evil shall befall you, nor shall any plague come near your dwelling; for He shall give His angels charge over you, to keep you in all your ways. In their hands they shall bear you up, lest you dash your foot against a stone.” Psalm 91:9-12

“The angel of The LORD encamps around those who fear Him, and He delivers them.” Psalm 34:7

“Have You not placed a hedge on every side around him and his household and all that he owns? You have blessed the work of his hands, and his possessions have increased in the land.” Job 1:10

“My God sent His angel and shut the mouths of the lions. They have not hurt me, for I was found innocent in His sight, and I have done no wrong against you, O king.” Daniel 6:22

“See that you do not despise one of these little ones, for I say to you that their angels in heaven continually see the face of My Father who is in heaven.” Matthew 18:10