Notwithstanding, in spite of, despite are often interchangeable prepositions.
Notwithstanding, the least emphatic, merely implies the presence of an obstacle; in spite of , the most emphatic, suggests active opposition or strongly adverse considerations to be encountered; despite is somewhat lighter in its emphasis than in spite of and otherwise is closer to notwithstanding than to in spite of <notwithstanding the rain, I shall go> <I shall go in spite of all your efforts to prevent me> <despite his assurances, I doubted him>