I am fully aware of what Luke 22:36 says. However, most of the time when Jesus spoke, people misunderstood him. When people thought he was talking about something physical, Jesus was actually talking about something spiritual. Like with Nicodemus thinking he needed to enter into his mother's womb a second time. Like with the disciples who stopped following Jesus because they thought Jesus wanted them to actually consume of his flesh and blood. For you must take note that Jesus said this before and not after Jesus rebuked Peter. For how many swords did they have? Just two. And Jesus said that was enough. Really? Are two swords enough to fight off the guards who were trying to arrest Jesus? No. They were not enough. Jesus said to Peter to put back his sword because he could call down a whole lot of angels to protect him (If he desired to do so). So Luke 22:36 is talking about making sure one has the Sword of the Spirit (Which is the Word of God, i.e. the Scriptures), it was not talking about an actual physical sword. For Jesus rebuking Peter shows that they misunderstood Him on this point.
This is the popular Christian belief but it is nowhere to be found within the lives of Jesus and the apostles, though. Nowhere did Jesus and the apostles ever use physical combat in delivering the gospel message. On the contrary, the apostles were persecuted, beaten, killed, imprisoned, and took punishment and they did dull out that punishment.
As for Romans 13:4: Who is the "he" who is being spoken of in verse 4? What does the context say?
" Let every soul be subject unto the higher powers . For there is no power but of God: the powers that be are ordained of God. Whosoever therefore resisteth the power, resisteth the ordinance of God: and they that resist shall receive to themselves damnation. For rulers are not a terror to good works, but to the evil. Wilt thou then not be afraid of the power? do that which is good, and thou shalt have praise of the same: For he is the minister of God to thee for good. But if thou do that which is evil, be afraid; for he beareth not the sword in vain: for he is the minister of God, a revenger to execute wrath upon him that doeth evil." (Romans 13:1-4).
Well, it says the the "he" in verse 4 is not reference to the believer but it is in reference to the higher powers, rulers, or government authorities (Like one's nation, it's armies, and police, etc.).
Paul says the weapons of our warefare are not carnal (2 Corinthians 10:4). Hence, why when he says we are to put on the whole armor of God in Ephesians 6, he was not talking about actual physical armor but spiritual armor. Paul mentions that we are to take up the Sword of the Spirit which is the Word of God. This is the same sword that Jesus was talking about.