The country faces a shortage of troops in the campaign against Russia's better equipped and larger military
The arrest of the suspect in his 30s brought calm back to the streets of the Bavarian capital after a tense morning. Police had asked residents to stay home until they find the attacker who had fled on a bicycle.
Munich police chief Hubertus Andrae told a news conference that eight people have been lightly injured in the attack and that the suspect was known to police from previous offences, including burglary.
"We have no indication of a terrorist, political, or religious motive," Andrae said. "I assume it is to do with a psychological disorder of the perpetrator."
Police had earlier said they believe the man, who attacked people at several different locations, acted alone.
His victims include a 12-year-old boy and a woman.