The more I work with teams, the more I think agile at any scale lives or dies based on attitudes of people in the organisation, rather than the scale at which you are attempting to do it.
Software development is hard, and it’s harder the greater the scale as Rachel’s post eloquently argues. However, I don’t think the scale is always the limiting factor here.
I’ve seen small teams with such a lack of trust that they burden themselves with suffocating process, and larger organisations with so much trust that they’re able to operate at the speed of organisations a quarter of their size.
As organisations get bigger, the trust required gets greater. If the trust exists, teams are able to remain independent and don’t get burdened with process.
If you need to work at one thing to make your large organisation more agile, work on building trust between teams, and between teams and management. Try small wins, quick feedback, and constant celebration. Decentralise decisions, give people ownership in their areas, and act like they’re as good as you know they are.
If middle and upper management could be persuaded to give up control and provide leadership instead, your scale matters much less than you might think.