Complex sentence: Apart from a few isolated victories, the war had not gone well for Britain since 1754 and in all theatres except India and North America (where Pitt's strategy had led to important gains in 1758) they were on the retreat.
Split into simpler sentences: Apart from a few isolated victories, the war had not gone well for Britain since 1754. In all theatres except India and North America (where Pitt's strategy had led to important gains in 1758) they were on the retreat.