Valmiki Ramayana Yuddha Kanda Sarga 35 Shloka 9

हीयमानेन when losing strength, समेवच with equal, राज्ञा with king, सन्धिः join, कर्तव्यः duty, शत्रुम् with enemy, नअवमन्येत not disrespecting, ज्यायान् quitting, विग्रहम् hostility, कुर्वीत do.

"When a king is losing strength, he should join hand s with the enemy who is equal to him. He should not disrespect the enemy but quit his hostility and join him (if the enemy is more powerful)."