Invocations for when you meet an adversary or a powerful ruler
اَللّٰهُـمَّ أَنْتَ عَضُدِيْ، وَأَنْتَ نَصِيْرِيْ، بِكَ أَجُوْلُ وَبِكَ أَصُوْلُ وَبِكَ أُقَاتِلُ
O Allah, You are my supporter and You are my helper, by You I move and by You I attack and by You I battle.
References
[Sunan Abu Dawud - 2632]