After its u-boats sank the lusitania in 1915, what did germany promise to do? stop fighting on the western front sign the treaty of brest-litovsk limit submarine warfare sink more passenger vessels

It's obvious, "Limit submarine warfare" because Germany could'nt ever win against the United States of America but this trategy of live was symbol of British people using Americans. Thus the Americans created plan to war with britian.

I hope I was a help