$webURL = "https://tenant.sharepoint.com/sites/PowershellTestingSite"
$adminUrl = "https://tenant-admin.sharepoint.com"
$userName = "user@tenant.onmicrosoft.com"
$members = "i:0#.f|membership|SecureUser@tenant.onmicrosoft.com"
# Let the user fill in their password in the PowerShell window
$password = ConvertTo-SecureString "tenantpassword" -AsPlainText -Force


$SPOCredentials = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($userName, $password)

# Creating client context object
$context = New-Object Microsoft.SharePoint.Client.ClientContext($webURL)
$context.credentials = $SPOCredentials
$web = $context.web
$context.load($web)

$web.breakroleinheritance($false, $false)
$web.update()

#send the request containing all operations to the server
try
{
    $context.executeQuery()
    write-host "info: Broken inheritance for $($web.title)" -foregroundcolor green
}
catch
{
    write-host "info: $($_.Exception.Message)" -foregroundcolor red
}