Hi there, 

I would try both, starting with the internal transfer. 

There is a high variability between offices in terms of how easy it is to transfer within firms. In some geographies (and especially if the office is large and language is not an issue), it's literally just a matter of paperwork and a couple of calls with HR and the office head. In others, it's a lot more complicated, requiring that you have both a push (current office is supporting the transfer) and an even stronger pull (a Partner from your desired office wants you there for a specific reason).

The short timeline makes it even more complicated. It's not impossible to get transferred after your first year, but it's rather unusual. Usually people do it after at least two years, and by then they have a clear value proposition and a good network of people in the target office to go the pull. 

So what I would advise is the following:

• Trigger the process internally, figuring out what are the requirements and timelines. Ask around your colleagues to see whether they know other people who did it and then connect with them to understand how. 
• Identify Partners in your target office and try to get staffed with them. This will make the transfer significantly easier because once they know they will support your application. 
• Give this entire process a couple of months and if there is no hope in sight and you're getting a lot of pushback, start applying at other firms in your target geography. 

Best of luck! This is not easy, but it's also not impossible.

Cristian