A messaging app called Signal based in San Francisco was used by the Trump administration to discuss war plans.

Top Trump administration officials used messaging app Signal to share war plans and mistakenly included a journalist in the encrypted chat, spurring calls by Democratic lawmakers for a congressional investigation into the security breach.

Here's what to know about the messaging app used by Trump Administration officials to discuss military strikes on Yemen.

The Trump administration sought to put the scandal over its use of the Signal messaging app behind it on Monday, calling it case closed, even as the breach provoked bipartisan criticism and opened up divisions inside the White House.

The Trump administration says it’s moving on from Signalgate — and that embattled national security adviser Mike Waltz is keeping his job. White House press secretary Karoline Leavitt told reporters Monday that the administration has decided to put the embarrassing scandal in the rear view mirror,

There are plenty of lingering questions about the "Signalgate" fiasco. Donald Trump and his White House team are no longer interested in getting answers.

"There have been steps made to ensure that something like that can obviously never happen again," Karoline Leavitt said.

White House press secretary Karoline Leavitt said Monday that national security adviser Mike Waltz continues to have President Donald Trump’s confidence and that it was done discussing the embarrassing matter of senior officials communicating about plans for an airstrike on a commercial messaging app.

When Donald Trump selected Mike Waltz to serve as national security adviser, the choice was widely seen as win-win: A combat veteran with four Bronze Stars would bring his judgment to the White House and his deep-red Florida House district was safe in Republican hands.