The Recession of '29 was the result of economic forces which, in our own time (OTL), led to the Great Depression, mass poverty and strikes in 1929 with the stock market crash.
in this timeline, Herbert Hoover vetoed the Smoot-Hawley Tariff act which would aggravate the depression. While the USA and Russian Federation escaped the worst of the recession, Europe was not so lucky. France collapsed into civil war and Martial Law was declared in the UK. In light of this, Germany seized the opportunity to rescind from the treaty of Versailles and sent Soldiers in to "restore order" (in reality, the civil war was started by Stasi agents). Rather than just restore order in France Germany totally annexed it.