Complex sentence: As detailed earlier, throughout the Winter of 1996, Soskovets' strategy was losing traction, and entirely ended when Yeltsin fired him as his campaign manager in the early days of Spring.
Split into simpler sentences: As detailed earlier, throughout the Winter of 1996, Soskovets' strategy was losing traction. The Strategy was entirely ended when Yeltsin fired him as his campaign manager in the early days of Spring.