Contradiction with Matthew 5:9
This verse promotes peace-making, whereas Joshua 1:11 prepares people for war by instructing them to get ready to possess the land.
Matthew 5:9: Blessed [are] the peacemakers: for they shall be called the children of God.
Contradiction with Exodus 20:13
This commandment states "Thou shalt not kill," which contradicts with the preparation for battle implied in Joshua 1:11.
Exodus 20:13: Thou shalt not kill.
Contradiction with Isaiah 2:4
This verse envisions a time of peace with no war, contrasting the war preparation in Joshua 1:11.
Isaiah 2:4: And he shall judge among the nations, and shall rebuke many people: and they shall beat their swords into plowshares, and their spears into pruninghooks: nation shall not lift up sword against nation, neither shall they learn war any more. [pruninghooks: or, scythes]
Contradiction with Luke 6:27
Jesus instructs to love enemies and do good to those who hate, which is in contrast to preparing for conquest as in Joshua 1:11.
Luke 6:27: But I say unto you which hear, Love your enemies, do good to them which hate you,
Contradiction with Romans 12:18
Advises to live peaceably with all men, differing from the idea of preparing for conflict in Joshua 1:11.
Romans 12:18: If it be possible, as much as lieth in you, live peaceably with all men.
Contradiction with Proverbs 3:5
Emphasizes trust in God rather than preparation for a military campaign, as seen in Joshua 1:11.
Proverbs 3:5: Trust in the LORD with all thine heart; and lean not unto thine own understanding.