Congressional investigators pored through "thousands of documents," received written statements from 50 police officers who defended the Capitol and received testimony from a wide array of current and former officials who played a role in the security preparations and response.

READ: Bipartisan Senate report investigating January 6 Capitol attack

Here are six takeaways from the report and its recommendations, which were released on a bipartisan basis by the Senate Rules Committee and the Senate Homeland Security Committee.

Capitol Police were warned

The report concluded that the US Capitol Police's main intelligence unit "was aware of the potential for violence in the days and weeks ahead of January 6." Period.

The inquiry determined that USCP's "decentralized" intelligence operation meant some people saw these warnings while other officials were left in the dark.

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The Metropolitan Police Department in Washington, DC, told Capitol Police that hotel bookings roughly doubled in comparison to pro-Trump rallies in November and December, the Senate report said.

And that's why one of the first recommendations from the Senate report is to empower the Capitol Police chief to have unilateral authority to request military support in emergency situations.

It seems like a no-brainer, but for this to happen, Congress will need to pass a new law.

Embarrassing crunch-time failures

The Senate inquiry uncovered some embarrassing failures within the "civil disturbance unit" of the Capitol Police, which is essentially the force's riot police or emergency response squad.

The report said these were found on "message boards, social media, memes, or hashtags." But intelligence officials struggled with how aggressively to police political speech, and how to differentiate the real threats from typical internet nonsense.

"FBI and (Department of Homeland Security) officials stressed the difficulty in discerning constitutionally protected free speech versus actionable, credible threats of violence," the report said, noting that officials have said they need to make improvements and do better in the future.

Horrifying tales from the frontlines

We've already heard from many of the brave police officers who risked their lives defending the Capitol, including some who were injured and others who engaged in hand-to-hand combat.

Sources told CNN that to keep Republicans in the fold, the report avoided using the word "insurrection" to describe the attack.

Apparently, the Senate investigation was significantly watered down before it even started.

This is one the many reasons why so many Democrats, Republicans, former US officials, national security experts, and US Capitol Police officers agree that there should be an independent commission to investigate January 6.