This verse was revealed in Madinah (Mawdudi and Dr. Muhammad Asad)
“Those who wait [and watch] you. Then if you gain a victory from Allah, they say, “Were we not with you?” But if the disbelievers have a success, they say [to them], “Did we not gain the advantage over you, but we protected you from the believers?” Allah will judge between [all of] you on the Day of Resurrection, and never will Allah give the disbelievers over the believers a way [to overcome them].” – Quran 4:141
This verse speaks about the hypocrites 1400 years ago, how they would wait and see. So when God Almighty gave victory to the Muslims i.e., defeated the hostile enemies, these hypocrites would come over to the believers and say ‘didn’t we help’ in defeating the enemy.
But when the enemy were victories they would say, ‘didn’t we encourage you not to surrender or give up fighting the Muslims?’. These hypocrites were playing both sides. God says here that he will bring these wrongdoers to judgement on the day of reckoning.
“156 Lit., “did we not gain mastery over you [i.e., “over your hearts” – cf. Lane II, 664] and defend you against the believers?” The term “believers” has obviously a sarcastic implication here, which justifies the use of the demonstrative pronoun “those” instead of the definite article “the”.
157 This announcement has, of course, a purely spiritual meaning, and does not necessarily apply to the changing fortunes of life – since (as this very verse points out) “those who deny the truth” may on occasion be “in luck”, that is to say, may gain temporal supremacy over the believers.” 
Sayyid Abul Ala Maududi:
“171 The hypocrites of every age have always enjoyed all the benefits conferred by Islam, by professing it with their tongue, and nominally joining the Muslim Community. At the same time they enjoy all the benefits they can derive from the disbelievers, by mixing with them and assuring them, “We are not bigoted Muslims though we are nominally connected with them.
We are akin to you in culture, in thoughts and in the way of life and our interests and loyalties are the same as yours. Therefore, you should rest assured that we will side with you in the conflict between Islam and kufr.” (Sayyid Abul Ala Maududi – Tafhim al-Qur’an – The Meaning of the Qur’an – online source)
“The passage then launches a strong campaign against the hypocrites, using a variety of tools. The hypocrites are those who continued with their hypocrisy as well as those who declared their unbelief after claiming to have accepted Islam. It describes the nature of hypocrisy, painting the ugly sights of what was perpetrated within the Muslim community. They would warmly welcome the believers when they were victorious,
but when victory went the way of the unbelievers, the hypocrites would try to impress on them that they themselves, [i.e. the hypocrites]. Had ensured that victory. They approached prayer very reluctantly, putting on a show of piety. They vacillated from one side to another, and their vacillation was indicative of their shiftiness.
Included within this campaign are a number of directives and cautions addressed to the believers, which indicates the extent of the damage the hypocrites caused. From these we can understand how large a force the hypocrites represented and how far they could penetrate into the Muslim community and affect its overall situation.
We should remember that this campaign had to take into consideration the realities of the Muslim community’s situation at the time as also the need to take it by the hand and isolate it from the hypocrites.
Hence, the believers are directed to avoid the hypocrites’ social gatherings where the latter often ridiculed God’s revelations stating that they did not believe in them. The believers were not commanded to impose a direct and complete boycott of the hypocrites. This indicates that there was a strong front of hypocrites able to move within the Muslim community in a way that rendered such a boycott either impartial or impossible. …” 
Scholar Abdullah Yusuf Ali:
“650 The methods and motives of Hypocrisy are thoroughly unmasked here. It has no principles, but watches for an opportunity to turn any event to its own advantage. If battle is joined between two inconsistent principles, it has no belief in either, but watches the result.
There is unceasing fight between Good and Evil in this world. If the Good seems to win, the hypocrites range themselves on its side with unctuous words, taking a great part of the credit to themselves. Perhaps the balance tips the other way later, and they have to make their peace with Evil.
‘Oh!’ they say, we were in the ranks of your enemy before, on purpose to protect you when they were too strong for you!’ This may suit the ways of the world. But the day of their account will come eventually. For the Good must ultimately triumph.” 
 The Message of The Quran translated and explained by Muhammad Asad, page 200
 In The Shade Of The Qur’an (‘Fi Dhilal Al Qur’an’) by Sayyid Qutb, volume 3, page 287 – 288
 The Meaning Of The Noble Qur’an, by Abdullah Yusuf Ali, page 63 – 64