How did the Germans defeat Varus, in 9 AD? Who led the Germans? What tribe(s) were involved?

The Germans led Varus inland. Then, when comfortable and secure in the friendliness of the inhabitants, Varus spread his troops out, as requested by the Germans, to help local communities with such things as robbers and escorting trains of provisions.

Two of the leading German conspirators, Arminius (a Romanized name of a Cherusci leader) and Segimerus, stayed with Varus, acting friendly and complacent. Meanwhile, there was an uprising in an area distant from where Arminius had brought Varus; so Varus, leading his troops, set out to quell the disturbance. Arminius and Segimerus excused themselves saying they would be gathering their own troops to help Varus. In reality, they were gathering troops, but not to help. The Roman soldiers who had not been dispatched to (and killed by) the small communities, with all their armor and heavy baggage, headed out through the Teutoberg Forest to assist in the uprising. Dio says bad weather and terrain hindered their progress. Attacked by the lighter armed forces of the Germans led by Arminius, the Roman leaders soon realized how disastrous their situation was. Varus did what the Romans considered the honorable thing: he committed suicide.

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