  The high design luminosity of the SuperKEKB electron-positron collider will
result in challenging levels of beam-induced backgro\ unds in the interaction
region. Understanding and mitigating these backgrounds is critical to the
success of the Belle~II experi\ ment. We report on the first background
measurements performed after roll-in of the Belle II detector, a period known
as SuperKE\ KB Phase 2, utilizing both the BEAST II system of dedicated
background detectors and the Belle II detector itself. We also repor\ t on
first revisions to the background simulation made in response to our findings.
Backgrounds measured include contributions f\ rom synchrotron radiation,
beam-gas, Touschek, and injection backgrounds. At the end of Phase 2,
single-beam backgrounds origina\ ting from the 4 GeV positron Low Energy Ring
(LER) agree reasonably well with simulation, while backgrounds from the 7 GeV
elect\ ron High Energy Ring (HER) are approximately one order of magnitude
higher than simulation. We extrapolate these backgrounds for\ ward and conclude
it is safe to install the Belle II vertex detector.
